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Sample records for acid pfsa membranes

  1. Constitutive response and mechanical properties of PFSA membranes in liquid water

    NASA Astrophysics Data System (ADS)

    Kusoglu, Ahmet; Tang, Yaliang; Lugo, Melissa; Karlsson, Anette M.; Santare, Michael H.; Cleghorn, Simon; Johnson, William B.

    The mechanical properties and swelling behavior of perfluorosulfonic acid (PFSA) membranes in liquid water have been investigated using a custom-built, temperature-controlled water bath. Interestingly, the theoretical models of Mooney-Rivlin and Ogden for rubber elasticity are shown to reproduce the major features of the experimentally obtained stress-strain relationships. In addition, stress relaxation of the membrane subjected to a fixed strain at room temperature fits time-dependent constitutive models used to describe nonlinear rubber elasticity. Thus, the experimental results suggest that even though PFSA is not an elastomer, the constitutive models developed for rubber-like behavior can be used for describing the ex situ constitutive response of PFSA membranes with high water content. This response is in contrast to the constitutive behavior of PFSA membranes swollen in water vapor (e.g. humid air and consequently lower water absorption in the membrane) where studies have suggested constitutive behavior corresponding to that of semicrystalline polymers, including distinct features such as a linear regime followed by onset of nonlinearity.

  2. Water, proton, and oxygen transport in high IEC, short side chain PFSA ionomer membranes: consequences of a frustrated network.

    PubMed

    Luo, Xiaoyan; Holdcroft, Steven; Mani, Ana; Zhang, Yongming; Shi, Zhiqing

    2011-10-28

    The effect of ion exchange capacity (IEC) on the water sorption properties of high IEC, short side chain (SSC) PFSA ionomer membranes, and the relationships between water content, proton conductivity, proton mobility, water permeation, oxygen diffusion, and oxygen permeation are investigated. SSC PFSA ionomer membranes possessing 1.3, 1.4, and 1.5 mmol g(-1) IEC are compared to a series of long side chain (LSC) PFSA ionomer membranes ranging in IEC from 0.9 to 1.13 mmol g(-1). At 25 °C, fully-hydrated SSC ionomer membranes are characterized as possessing higher water contents (56-75 vol%), moderate λ values (15-18), high analytical acid concentrations (2-2.8 M), and moderate conductivity (88-115 mS/cm); but lower than anticipated effective proton mobility. Complementary measurements of water permeability, oxygen diffusion, and oxygen permeability also yield lower than expected values given their much higher water contents. Potential benefits afforded by reducing the side chain length of PFSA ionomer membranes, such as increased crystallinity, higher IEC, and high hydrated acid concentration are offset by a less-developed, frustrated hydrophilic percolation network, which provides a motivation for future improvements of transport properties for this class of material.

  3. EFFECT OF COMPRESSION ON CONDUCTIVITY AND MORPHOLOGY OF PFSA MEMBRANES

    SciTech Connect

    Kusoglu, Ahmet; Weber, Adam; Jiang, Ruichin; Gittleman, Craig

    2011-07-20

    Polymer-Electrolyte-Fuel-Cells (PEFCs) are promising candidates for powering vehicles and portable devices using renewable-energy sources. The core of a PEFC is the solid electrolyte membrane that conducts protons from anode to cathode, where water is generated. The conductivity of the membrane, however, depends on the water content of the membrane, which is strongly related to the cell operating conditions. The membrane and other cell components are typically compressed to minimize various contact resistances. Moreover, the swelling of a somewhat constrained membrane in the cell due to the humidity changes generates additional compressive stresses in the membrane. These external stresses are balanced by the internal swelling pressure of the membrane and change the swelling equilibrium. It was shown using a fuel-cell setup that compression could reduce the water content of the membrane or alter the cell resistance. Nevertheless, the effect of compression on the membrane’s transport properties is yet to be understood, as well as its implications in the structure-functions relationships of the membrane. We previously studied, both experimentally and theoretically, how compression affects the water content of the membrane.6 However, more information is required the gain a fundamental understanding of the compression effects. In this talk, we present the results of our investigation on the in-situ conductivity of the membrane as a function of humidity and cell compression pressure. Moreover, to better understand the morphology of compressed membrane, small-angle X-ray-scattering (SAXS) experiments were performed. The conductivity data is then analyzed by investigating the size of the water domains of the compressed membrane determined from the SAXS measurements.

  4. Brain region-specific perfluoroalkylated sulfonate (PFSA) and carboxylic acid (PFCA) accumulation and neurochemical biomarker responses in east Greenland polar bears (Ursus maritimus).

    PubMed

    Eggers Pedersen, Kathrine; Basu, Niladri; Letcher, Robert; Greaves, Alana K; Sonne, Christian; Dietz, Rune; Styrishave, Bjarne

    2015-04-01

    Perfluoroalkyl substances (PFASs) is a growing class of contaminants in the Arctic environment, and include the established perfluorinated sulfonates (PFSAs; especially perfluorooctane sulfonate (PFOS)) and carboxylic acids (PFCAs). PFSAs and PFCAs of varying chain length have been reported to bioaccumulate in lipid rich tissues of the brain among other tissues such as liver, and can reach high concentrations in top predators including the polar bear. PFCA and PFSA bioaccummulation in the brain has the potential to pose neurotoxic effects and therefore we conducted a study to investigate if variations in neurochemical transmitter systems i.e. the cholinergic, glutaminergic, dopaminergic and GABAergic, could be related to brain-specific bioaccumulation of PFASs in East Greenland polar bears. Nine brain regions from nine polar bears were analyzed for enzyme activity (monoamine oxidase (MAO), acetylcholinesterase (AChE) and glutamine synthetase (GS)) and receptor density (dopamine-2 (D2), muscarinic cholinergic (mAChR) and gamma-butyric acid type A (GABA-A)) along with PFSA and PFCA concentrations. Average brain ∑PFSA concentration was 25ng/g ww where PFOS accounted for 91%. Average ∑PFCA concentration was 88ng/g ww where PFUnDA, PFDoDA and PFTrDA combined accounted for 79%. The highest concentrations of PFASs were measured in brain stem, cerebellum and hippocampus. Correlative analyses were performed both across and within brain regions. Significant positive correlations were found between PFASs and MAO activity in occipital lobe (e.g. ∑PFCA; rp=0.83, p=0.041, n=6) and across brain regions (e.g. ∑PFCA; rp=0.47, p=0.001, ∑PFSA; rp=0.44, p>0.001; n=50). GABA-A receptor density was positively correlated with two PFASs across brain regions (PFOS; rp=0.33, p=0.02 and PFDoDA; rp=0.34, p=0.014; n=52). Significant negative correlations were found between mAChR density and PFASs in cerebellum (e.g. ∑PFCA; rp=-0.95, p=0.013, n=5) and across brain regions (e.g.

  5. Brain region-specific perfluoroalkylated sulfonate (PFSA) and carboxylic acid (PFCA) accumulation and neurochemical biomarker responses in east Greenland polar bears (Ursus maritimus).

    PubMed

    Eggers Pedersen, Kathrine; Basu, Niladri; Letcher, Robert; Greaves, Alana K; Sonne, Christian; Dietz, Rune; Styrishave, Bjarne

    2015-04-01

    Perfluoroalkyl substances (PFASs) is a growing class of contaminants in the Arctic environment, and include the established perfluorinated sulfonates (PFSAs; especially perfluorooctane sulfonate (PFOS)) and carboxylic acids (PFCAs). PFSAs and PFCAs of varying chain length have been reported to bioaccumulate in lipid rich tissues of the brain among other tissues such as liver, and can reach high concentrations in top predators including the polar bear. PFCA and PFSA bioaccummulation in the brain has the potential to pose neurotoxic effects and therefore we conducted a study to investigate if variations in neurochemical transmitter systems i.e. the cholinergic, glutaminergic, dopaminergic and GABAergic, could be related to brain-specific bioaccumulation of PFASs in East Greenland polar bears. Nine brain regions from nine polar bears were analyzed for enzyme activity (monoamine oxidase (MAO), acetylcholinesterase (AChE) and glutamine synthetase (GS)) and receptor density (dopamine-2 (D2), muscarinic cholinergic (mAChR) and gamma-butyric acid type A (GABA-A)) along with PFSA and PFCA concentrations. Average brain ∑PFSA concentration was 25ng/g ww where PFOS accounted for 91%. Average ∑PFCA concentration was 88ng/g ww where PFUnDA, PFDoDA and PFTrDA combined accounted for 79%. The highest concentrations of PFASs were measured in brain stem, cerebellum and hippocampus. Correlative analyses were performed both across and within brain regions. Significant positive correlations were found between PFASs and MAO activity in occipital lobe (e.g. ∑PFCA; rp=0.83, p=0.041, n=6) and across brain regions (e.g. ∑PFCA; rp=0.47, p=0.001, ∑PFSA; rp=0.44, p>0.001; n=50). GABA-A receptor density was positively correlated with two PFASs across brain regions (PFOS; rp=0.33, p=0.02 and PFDoDA; rp=0.34, p=0.014; n=52). Significant negative correlations were found between mAChR density and PFASs in cerebellum (e.g. ∑PFCA; rp=-0.95, p=0.013, n=5) and across brain regions (e.g.

  6. A Review of Molecular-Level Mechanism of Membrane Degradation in the Polymer Electrolyte Fuel Cell

    PubMed Central

    Ishimoto, Takayoshi; Koyama, Michihisa

    2012-01-01

    Chemical degradation of perfluorosulfonic acid (PFSA) membrane is one of the most serious problems for stable and long-term operations of the polymer electrolyte fuel cell (PEFC). The chemical degradation is caused by the chemical reaction between the PFSA membrane and chemical species such as free radicals. Although chemical degradation of the PFSA membrane has been studied by various experimental techniques, the mechanism of chemical degradation relies much on speculations from ex-situ observations. Recent activities applying theoretical methods such as density functional theory, in situ experimental observation, and mechanistic study by using simplified model compound systems have led to gradual clarification of the atomistic details of the chemical degradation mechanism. In this review paper, we summarize recent reports on the chemical degradation mechanism of the PFSA membrane from an atomistic point of view. PMID:24958288

  7. Promising aquivion composite membranes based on fluoroalkyl zirconium phosphate for fuel cell applications.

    PubMed

    Donnadio, Anna; Pica, Monica; Subianto, Surya; Jones, Deborah J; Cojocaru, Paula; Casciola, Mario

    2014-08-01

    Layered zirconium phosphate (ZP) that bears fluorinated alkyl chains bonded covalently to the layers (ZPR) was used as a nanofiller in membranes based on a short-side-chain perfluorosulfonic acid (PFSA) to mechanically reinforce the PFSA hydrophobic component. Compared to the pristine PFSA, membranes with a ZPR loading up to 30 wt% show enhanced mechanical properties, and the largest improvement of elastic modulus (E) and yield stress (σY ) are observed for the 10 wt% ZPR membrane: ΔE/E up to 90% and ΔσY /σY up 70% at 70°C and 80% relative humidity (RH). In the RH range 50-95%, the in-plane conductivity of the composite membranes reaches 0.43 S cm(-1) for 10 wt% ZPR at 110°C and is on average 30% higher than the conductivity of the pristine PFSA. The 10 wt % ZPR membrane is as hydrated as the neat PFSA membrane at 50% RH but becomes progressively less hydrated with increasing RH both at 80 and 110°C. The fuel cell performance of this membrane, at 80°C and 30% RH, is better than that of the unmodified PFSA.

  8. Impact of hygrothermal aging on structure/function relationship of perfluorosulfonic-acid membrane

    DOE PAGES

    Shi, Shouwen; Dursch, Thomas J.; Blake, Colin; Mukundan, Rangachary; Borup, Rodney L.; Weber, Adam Z.; Kusoglu, Ahmet

    2015-10-20

    Perfluorosulfonic-acid (PFSA) membranes are widely used as the solid electrolyte in electrochemical devices where their main functionalities are ion (proton) conduction and gas separation in a thermomechanically stable matrix. Due to prolonged operational requirements in these devices, PFSA membranes’ properties change with time due to hygrothermal aging. This paper studies the evolution of PFSA structure/property relationship changes during hygrothermal aging, including chemical changes leading to changes in ion-exchange capacity (IEC), nanostructure, water-uptake behavior, conductivity, and mechanical properties. Our findings demonstrate that with hygrothermal aging, the storage modulus increases, while IEC and water content decrease, consistent with the changes in nanostructure,more » that is, water- and crystalline-domain spacings inferred from small- and wide-angle X-ray scattering (SAXS/WAXS) experiments. In addition, the impact of aging is found to depend on the membrane's thermal prehistory and post-treatments, although universal correlations exist between nanostructural changes and water uptake. Lastly, the findings have impact on understanding lifetime, durability, and use of these and related polymers in various technologies.« less

  9. Impact of hygrothermal aging on structure/function relationship of perfluorosulfonic-acid membrane

    SciTech Connect

    Shi, Shouwen; Dursch, Thomas J.; Blake, Colin; Mukundan, Rangachary; Borup, Rodney L.; Weber, Adam Z.; Kusoglu, Ahmet

    2015-10-20

    Perfluorosulfonic-acid (PFSA) membranes are widely used as the solid electrolyte in electrochemical devices where their main functionalities are ion (proton) conduction and gas separation in a thermomechanically stable matrix. Due to prolonged operational requirements in these devices, PFSA membranes’ properties change with time due to hygrothermal aging. This paper studies the evolution of PFSA structure/property relationship changes during hygrothermal aging, including chemical changes leading to changes in ion-exchange capacity (IEC), nanostructure, water-uptake behavior, conductivity, and mechanical properties. Our findings demonstrate that with hygrothermal aging, the storage modulus increases, while IEC and water content decrease, consistent with the changes in nanostructure, that is, water- and crystalline-domain spacings inferred from small- and wide-angle X-ray scattering (SAXS/WAXS) experiments. In addition, the impact of aging is found to depend on the membrane's thermal prehistory and post-treatments, although universal correlations exist between nanostructural changes and water uptake. Lastly, the findings have impact on understanding lifetime, durability, and use of these and related polymers in various technologies.

  10. Influence of Substrate on PFSA Thin-Film Morphology

    NASA Astrophysics Data System (ADS)

    Dudenas, Peter; Kusoglu, Ahmet; Venkatakrishnan, Singanallur; Hexemer, Alexander; Weber, Adam

    Perfluorosulfonic-acid (PFSA) ionomers are the most commonly used electrolyte for polymer-electrolyte fuel cells (PEFCs) due to their high conductivity and good electrochemical and thermo-mechanical stability. A PFSA's chemical structure is comprised of a polytetrafluoroethylene (PTFE) backbone that provides mechanical and chemical stability, and randomly placed tethered perfluoroether side chains terminated with sulfonic-acid groups, which impart its remarkable proton-conduction capabilities. Controlled by substrate/film interactions, long-range structural order in PFSAs change when confined to thin films (<200 nm), as does its transport and mechanical properties. The nature of change is substrate dependent, where stronger interactions create a more dramatic change in properties. In this talk, grazing-incidence c-Ray scattering (GIXS) is used to demonstrate induced structural order on metallic substrates, which is not present on other substrates like silicon and carbon. The higher degree of ordering is correlated with measured changes in mechanical properties for the thin films. Scattering data is also modeled using the recently released program high-performance GISAXS (HipGISAXS), to estimate the size and distribution of the ordered domains. -/a

  11. Immobilized transition metal-based radical scavengers and their effect on durability of Aquivion® perfluorosulfonic acid membranes

    NASA Astrophysics Data System (ADS)

    D'Urso, C.; Oldani, C.; Baglio, V.; Merlo, L.; Aricò, A. S.

    2016-01-01

    A simple and broadly applicable preparation procedure to obtain silica-supported transition metal (namely Cr, Co and Mn)-based radical scavengers, containing sulfonic acid functionalities, is reported. These systems are widely characterised in terms of structure, bulk and surface composition and morphology by X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), X-Ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The scavenger material is loaded in ePTFE reinforced membranes prepared from Aquivion® perfluorosulfonic acid (PFSA) dispersions. All these composite membranes show longer lifetime in Accelerated Stress Tests (AST) and reduced fluoride release in Fenton's tests than the scavenger-free membranes without any loss in electrochemical performance. The Cr-scavenger-based polymer electrolyte shows a three-time larger stability than the pristine membrane.

  12. Electrospun Nafion®/Polyphenylsulfone composite membranes for regenerative Hydrogen bromine fuel cells

    DOE PAGES

    Park, Jun; Wycisk, Ryszard; Pintauro, Peter N.; Yarlagadda, Venkata; Van Nguyen, Trung

    2016-02-29

    Here, the regenerative H2/Br2-HBr fuel cell, utilizing an oxidant solution of Br2 in aqueous HBr, shows a number of benefits for grid-scale electricity storage. The membrane-electrode assembly, a key component of a fuel cell, contains a proton-conducting membrane, typically based on the perfluorosulfonic acid (PFSA) ionomer. Unfortunately, the high cost of PFSA membranes and their relatively high bromine crossover are serious drawbacks. Nanofiber composite membranes can overcome these limitations. In this work, composite membranes were prepared from electrospun dual-fiber mats containing Nafion® PFSA ionomer for facile proton transport and an uncharged polymer, polyphenylsulfone (PPSU), for mechanical reinforcement, and swelling control.more » After electrospinning, Nafion/PPSU mats were converted into composite membranes by softening the PPSU fibers, through exposure to chloroform vapor, thus filling the voids between ionomer nanofibers. It was demonstrated that the relative membrane selectivity, referenced to Nafion® 115, increased with increasing PPSU content, e.g., a selectivity of 11 at 25 vol% of Nafion fibers. H2-Br2 fuel cell power output with a 65 m thick membrane containing 55 vol% Nafion fibers was somewhat better than that of a 150 m Nafion® 115 reference, but its cost advantage due to a four-fold decrease in PFSA content and a lower bromine species crossover make it an attractive candidate for use in H2/Br2-HBr systems.« less

  13. Acid diffusion through polyaniline membranes

    SciTech Connect

    Su, T.M.; Huang, S.C.; Conklin, J.A.

    1995-12-01

    Polyaniline membranes in the undoped (base) and doped (acid) forms are studied for their utility as pervaporation membranes. The separation of water from mixtures of propionic acid, acetic acid and formic acid have been demonstrated from various feed compositions. Doped polyaniline displays an enhanced selectivity of water over these organic acids as compared with undoped polyaniline. For as-cast polyaniline membranes a diffusion coefficient (D) on the order of 10{sup -9} cm{sup 2}/sec has been determined for the flux of protons through the membranes using hydrochloric acid.

  14. Investigation of Humidity Dependent Surface Morphology and Proton Conduction in Multi-Acid Side Chain Membranes by Conductive Probe Atomic Force Microscopy.

    PubMed

    Economou, Nicholas J; Barnes, Austin M; Wheat, Andrew J; Schaberg, Mark S; Hamrock, Steven J; Buratto, Steven K

    2015-11-01

    In this report, we employ phase-contrast tapping mode and conductive probe atomic force microscopy (cp-AFM) as tools to investigate the nanoscale morphology and proton conductance of a 3M perfluoro-imide acid (PFIA) membrane (625 EW) over a large range of relative humidity (3-95% RH). As a point of comparison, we also investigate 3M perfluorosulfonic acid (PFSA) (825 EW) and Nafion 212. With AFM, we assess the membrane's water retention and mechanical stability at low RH and high RH, respectively. Cp-AFM allows us to spatially resolve the hydrophilic and electrochemically active domains under a similar set of conditions and observe directly the ties between membrane morphology and proton conductance. From our data, we are able to correlate the improved water retention indicated by the size of the hydrophilic domains with the proton conductance in the PFIA membrane at elevated temperature and compare the result with that observed for the PFSA and Nafion. At high RH conditions, we see evidence of a nearly continuous hydrophilic phase, which indicates a high degree of swelling. PMID:26439098

  15. An experimental investigation of strain rate, temperature and humidity effects on the mechanical behavior of a perfluorosulfonic acid membrane

    NASA Astrophysics Data System (ADS)

    Lu, Zongwen; Lugo, Melissa; Santare, Michael H.; Karlsson, Anette M.; Busby, F. Colin; Walsh, Peter

    2012-09-01

    The time-dependent hygro-thermal mechanical behavior of a perfluorosulfonic acid (PFSA) membrane (Nafion® 211 membrane) commonly used in Proton Exchange Membrane Fuel Cells (PEMFCs) is investigated at selected strain rates for a broad range of temperatures and humidities. Tensile tests and relaxation tests are conducted to determine Young's modulus and proportional limit stress as functions of strain rate, temperature and humidity. The results show that Young's modulus and proportional limit stress increase as the strain rate increases, and decrease as the temperature or humidity increases. The results also show that the mechanical response of Nafion® 211 membrane is more sensitive to typical changes in strain rate or temperature than to typical changes in humidity. In addition, two temperature/humidity cycles are conducted to determine the steady state swelling behavior of Nafion® 211 membrane as a function of temperature and humidity. The results show that the membrane swells with increasing temperature and humidity, and that there is little or no hygro-thermal history effect for the swelling strains.

  16. QENS investigation of proton confined motions in hydrated perfluorinated sulfonic membranes and self-assembled surfactants

    NASA Astrophysics Data System (ADS)

    Berrod, Quentin; Lyonnard, Sandrine; Guillermo, Armel; Ollivier, Jacques; Frick, Bernhard; Gébel, Gérard

    2015-01-01

    We report on QuasiElastic Neutron Scattering (QENS) investigations of the dynamics of protons and water molecules confined in nanostructured perfluorinated sulfonic acid (PFSA) materials, namely a commercial Aquivion membrane and the perfluorooctane sulfonic acid (PFOS) surfactant. The former is used as electrolyte in low-temperature fuel cells, while the latter forms mesomorphous self-assembled phases in water. The dynamics was investigated as a function of the hydration level, in a wide time range by combining time-of-flight and backscattering incoherent QENS experiments. Analysis of the quasielastic broadening revealed for both systems the existence of localized translational diffusive motions, fast rotational motions and slow hopping of protons in the vicinity of the sulfonic charges. The characteristic times and diffusion coefficients have been found to exhibit a very similar behaviour in both membrane and surfactant structures. Our study provides a comprehensive picture of the proton motion mechanisms and the dynamics of confined water in model and real PFSA nanostructures.

  17. Effect of cation contamination and hydrated pressure loading on the mechanical properties of proton exchange membranes

    NASA Astrophysics Data System (ADS)

    Jia, Ruiliang; Han, Binghong; Levi, Kemal; Hasegawa, Takuya; Ye, Jiping; Dauskardt, Reinhold H.

    Perfluorosulfonic acid (PFSA) polymer membranes are widely used as electrolyte thin films to transport protons in proton exchange membrane (PEM) fuel cells. The mechanical degradation of the membrane represents a common failure mode that limits the operational life of the fuel cells. In the present work, effect of contamination related to cation exchange on the mechanical reliability of PEMs was investigated. We applied the bulge test technique to assess the mechanical properties of Nafion ® PFSA membranes simulating pressure loading on hydrated PEMs in fuel cells. The corresponding elastic moduli of Nafion ® before and after cation exchange were analyzed and compared with the results measured by uniaxial tension experiments at selected humidity conditions, showing increasing stiffness with the increase of cation radius. We also used the out-of-plane tearing test method to characterize the fracture behaviors of PEMs. The effects of cation exchange and water absorption on mechanical and fracture properties of PEMs at different temperatures are discussed in terms of cation and water interactions with the molecular structure of PFSA polymers.

  18. Effects of dielectric saturation and ionic screening on the proton self-diffusion coefficients in perfluorosulfonic acid membranes

    NASA Astrophysics Data System (ADS)

    Paul, Reginald; Paddison, Stephen J.

    2005-12-01

    Proton transport in perfluorosulfonic acid (PFSA) membranes is investigated through a statistical mechanical model that includes the effects of the interaction of the tethered sulfonate groups with both the water and solvated protons. We first derive a potential that describes the electrostatic field due to the dissociated sulfonic acid groups by extending the work of Grønbech-Jensen et al. [Grønbech-Jensen et al. Mol. Phys. 92, 941 (1997)] to a finite array of point charges. A highly convergent series is obtained which includes the effects of screening due to the protons. We then investigate the effects of both dielectric saturation and two distinct formulations of ionic screening on the proton self-diffusion coefficient in Nafion membranes over a range of water contents. Our computations show that the two phenomena (i.e., dielectric saturation and ionic screening) under constant temperature conditions result in canceling affects. Our calculations provide a radial dependence of the proton mobility suggesting that the dominant self-diffusion occurs in the central region of the pores, well separated from the sulfonate groups. Through comparison of our calculated diffusion coefficients with the experimental values we derived a slightly smaller average separation distance of the hydronium ion from the sulfonate ions than suggested by either electronic structure calculations or multistate empirical valence bond molecular-dynamics simulations.

  19. EVALUATION OF PROTON-CONDUCTING MEMBRANES FOR USE IN A SULFUR-DIOXIDE DEPOLARIZED ELECTROLYZER

    SciTech Connect

    Hobbs, D.; Elvington, M.; Colon-Mercado, H.

    2009-11-11

    The chemical stability, sulfur dioxide transport, ionic conductivity, and electrolyzer performance have been measured for several commercially available and experimental proton exchange membranes (PEMs) for use in a sulfur dioxide depolarized electrolyzer (SDE). The SDE's function is to produce hydrogen by using the Hybrid Sulfur (HyS) Process, a sulfur based electrochemical/thermochemical hybrid cycle. Membrane stability was evaluated using a screening process where each candidate PEM was heated at 80 C in 60 wt. % H{sub 2}SO{sub 4} for 24 hours. Following acid exposure, chemical stability for each membrane was evaluated by FTIR using the ATR sampling technique. Membrane SO{sub 2} transport was evaluated using a two-chamber permeation cell. SO{sub 2} was introduced into one chamber whereupon SO{sub 2} transported across the membrane into the other chamber and oxidized to H{sub 2}SO{sub 4} at an anode positioned immediately adjacent to the membrane. The resulting current was used to determine the SO{sub 2} flux and SO{sub 2} transport. Additionally, membrane electrode assemblies (MEAs) were prepared from candidate membranes to evaluate ionic conductivity and selectivity (ionic conductivity vs. SO{sub 2} transport) which can serve as a tool for selecting membranes. MEAs were also performance tested in a HyS electrolyzer measuring current density versus a constant cell voltage (1V, 80 C in SO{sub 2} saturated 30 wt% H2SO{sub 4}). Finally, candidate membranes were evaluated considering all measured parameters including SO{sub 2} flux, SO{sub 2} transport, ionic conductivity, HyS electrolyzer performance, and membrane stability. Candidate membranes included both PFSA and non-PFSA polymers and polymer blends of which the non-PFSA polymers, BPVE-6F and PBI, showed the best selectivity.

  20. FY08 MEMBRANE CHARACTERIZATION REPORT FOR HYBRID SULFUR ELECTROLYZER

    SciTech Connect

    Hobbs, D; Hector Colon-Mercado, H; Mark Elvington, M

    2008-09-01

    This report summarizes results from all of the membrane testing completed to date at the Savannah River National Laboratory (SRNL) for the sulfur dioxide-depolarized electrolyzer (SDE). Several types of commercially-available membranes have been analyzed for ionic resistance and sulfur dioxide transport including perfluorinated sulfonic acid (PFSA), sulfonated polyether-ketone-ketone (SPEKK), and polybenzimidazole membranes (PBI). Of these membrane types, the poly-benzimidazole membrane, Celtec-L, exhibited the best combination of characteristics for use in an SDE. Several experimental membranes have also been analyzed including hydrated sulfonated Diels-Alder polyphenylenes (SDAPP) membranes from Sandia National Laboratory, perfluorosulfonimide (PFSI) and sulfonated perfluorocyclobutyl aromatic ether (S-PFCB) prepared by Clemson University, hydrated platinum-treated PFSA prepared by Giner Electrochemical Systems (GES) and Pt-Nafion{reg_sign} 115 composites prepared at SRNL. The chemical stability, SO{sub 2} transport and ionic conductivity characteristics have been measured for several commercially available and experimental proton-conducting membranes. Commercially available PFSA membranes such as the Nafion{reg_sign} series exhibited excellent chemical stability and ionic conductivity in sulfur dioxide saturated sulfuric acid solutions. Sulfur dioxide transport in the Nafion{reg_sign} membranes varied proportionally with the thickness and equivalent weight of the membrane. Although the SO{sub 2} transport in the Nafion{reg_sign} membranes is higher than desired, the excellent chemical stability and conductivity makes this membrane the best commercially-available membrane at this time. Initial results indicated that a modified Nafion{reg_sign} membrane incorporating Pt nanoparticles exhibited significantly reduced SO{sub 2} transport. Reduced SO{sub 2} transport was also measured with commercially available PBI membrane and several experimental membranes produced

  1. Proton Exchange Membranes for Fuel Cells

    SciTech Connect

    Devanathan, Ramaswami

    2010-11-01

    Proton exchange membrane, also known as polymer electrolyte membrane, fuel cells (PEMFCs) offer the promise of efficient conversion of chemical energy of fuel, such as hydrogen or methanol, into electricity with minimal pollution. Their widespread use to power zero-emission automobiles as part of a hydrogen economy can contribute to enhanced energy security and reduction in greenhouse gas emissions. However, the commercial viability of PEMFC technology is hindered by high cost associated with the membrane electrode assembly (MEA) and poor membrane durability under prolonged operation at elevated temperature. Membranes for automotive fuel cell applications need to perform well over a period comparable to the life of an automotive engine and under heavy load cycling including start-stop cycling under sub-freezing conditions. The combination of elevated temperature, changes in humidity levels, physical stresses and harsh chemical environment contribute to membrane degradation. Perfluorinated sulfonic acid (PFSA)-based membranes, such as Nafion®, have been the mainstay of PEMFC technology. Their limitations, in terms of cost and poor conductivity at low hydration, have led to continuing research into membranes that have good proton conductivity at elevated temperatures above 120 °C and under low humidity conditions. Such membranes have the potential to avoid catalyst poisoning, simplify fuel cell design and reduce the cost of fuel cells. Hydrocarbon-based membranes are being developed as alternatives to PFSA membranes, but concerns about chemical and mechanical stability and durability remain. Novel anhydrous membranes based on polymer gels infused with protic ionic liquids have also been recently proposed, but considerable fundamental research is needed to understand proton transport in novel membranes and evaluate durability under fuel cell operating conditions. In order to advance this promising technology, it is essential to rationally design the next generation

  2. Interaction of abscisic acid with phospholipid membranes

    SciTech Connect

    Stillwell, W.; Brengle, B.; Hester, P.; Wassall, S.T. )

    1989-04-04

    The plant hormone abscisic acid (ABA) is shown, under certain conditions, to greatly enhance the permeability of phospholipid bilayer membranes to the nonelectrolyte erythritol (followed spectrophotometrically by osmotic swelling) and the anion carboxyfluorescein (followed by fluorescence). The hormone is ineffective with single- and mixed-component phosphatidylcholine membranes in the liquid-crystalline or gel states. In contrast, substantial ABA-induced permeability is measured for two-component membranes containing lipids with different polar head groups or containing phosphatidylcholines with different acyl chains at temperatures where gel and liquid-crystalline phases coexist. Despite the large ABA-induced enhancement in bilayer permeability, no evidence for a substantial change at the molecular level was seen in the membranes by magnetic resonance techniques. {sup 13}C NMR spin-lattice relaxation times, T{sub 1}, in sonicated unilamellar vesicles and ESR of spin-labeled fatty acids intercalated into membranes showed negligible effect on acyl chain order and dynamics within the bilayer, while {sup 31}P NMR of sonicated unilamellar vesicles indicated negligible effect on molecular motion and conformation in the head-group region. The authors propose that, instead of causing a general nonspecific perturbation to the membrane, the hormone acts at membrane defects formed due to mismatch in molecular packing where two different head groups or acyl chain states interface. Increased membrane disruption by ABA at these points of membrane instability could then produce an enhancement in permeability.

  3. Numerical evaluation of crack growth in polymer electrolyte fuel cell membranes based on plastically dissipated energy

    NASA Astrophysics Data System (ADS)

    Ding, Guoliang; Santare, Michael H.; Karlsson, Anette M.; Kusoglu, Ahmet

    2016-06-01

    Understanding the mechanisms of growth of defects in polymer electrolyte membrane (PEM) fuel cells is essential for improving cell longevity. Characterizing the crack growth in PEM fuel cell membrane under relative humidity (RH) cycling is an important step towards establishing strategies essential for developing more durable membrane electrode assemblies (MEA). In this study, a crack propagation criterion based on plastically dissipated energy is investigated numerically. The accumulation of plastically dissipated energy under cyclical RH loading ahead of the crack tip is calculated and compared to a critical value, presumed to be a material parameter. Once the accumulation reaches the critical value, the crack propagates via a node release algorithm. From the literature, it is well established experimentally that membranes reinforced with expanded polytetrafluoroethylene (ePTFE) reinforced perfluorosulfonic acid (PFSA) have better durability than unreinforced membranes, and through-thickness cracks are generally found under the flow channel regions but not land regions in unreinforced PFSA membranes. We show that the proposed plastically dissipated energy criterion captures these experimental observations and provides a framework for investigating failure mechanisms in ionomer membranes subjected to similar environmental loads.

  4. Proton conducting membrane using a solid acid

    NASA Technical Reports Server (NTRS)

    Haile, Sossina M. (Inventor); Chisholm, Calum (Inventor); Boysen, Dane A. (Inventor); Narayanan, Sekharipuram R. (Inventor)

    2006-01-01

    A solid acid material is used as a proton conducting membrane in an electrochemical device. The solid acid material can be one of a plurality of different kinds of materials. A binder can be added, and that binder can be either a nonconducting or a conducting binder. Nonconducting binders can be, for example, a polymer or a glass. A conducting binder enables the device to be both proton conducting and electron conducting.

  5. Proton conducting membrane using a solid acid

    NASA Technical Reports Server (NTRS)

    Chisholm, Calum (Inventor); Narayanan, Sekharipuram R. (Inventor); Boysen, Dane (Inventor); Haile, Sossina M. (Inventor)

    2002-01-01

    A solid acid material is used as a proton conducting membrane in an electrochemical device. The solid acid material can be one of a plurality of different kinds of materials. A binder can be added, and that binder can be either a nonconducting or a conducting binder. Nonconducting binders can be, for example, a polymer or a glass. A conducting binder enables the device to be both proton conducting and electron conducting. The solid acid material has the general form M.sub.a H.sub.b (XO.sub.t).sub.c.

  6. Selectivity of Direct Methanol Fuel Cell Membranes.

    PubMed

    Aricò, Antonino S; Sebastian, David; Schuster, Michael; Bauer, Bernd; D'Urso, Claudia; Lufrano, Francesco; Baglio, Vincenzo

    2015-11-24

    Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion(®) were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate-PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion(®) 115-based MEA (77 mW·cm(-2) vs. 64 mW·cm(-2)). This result was due to a lower methanol crossover (47 mA·cm(-2) equivalent current density for s-PEEK vs. 120 mA·cm(-2) for Nafion(®) 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm² for s-PEEK vs. 0.22 Ohm cm² for Nafion(®) 115).

  7. Selectivity of Direct Methanol Fuel Cell Membranes

    PubMed Central

    Aricò, Antonino S.; Sebastian, David; Schuster, Michael; Bauer, Bernd; D’Urso, Claudia; Lufrano, Francesco; Baglio, Vincenzo

    2015-01-01

    Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion® were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate–PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion® 115-based MEA (77 mW·cm−2 vs. 64 mW·cm−2). This result was due to a lower methanol crossover (47 mA·cm−2 equivalent current density for s-PEEK vs. 120 mA·cm−2 for Nafion® 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm2 for s-PEEK vs. 0.22 Ohm cm2 for Nafion® 115). PMID:26610582

  8. Durable, Low-cost, Improved Fuel Cell Membranes

    SciTech Connect

    Chris Roger; David Mountz; Wensheng He; Tao Zhang

    2011-03-17

    The development of low cost, durable membranes and membranes electrode assemblies (MEAs) that operate under reduced relative humidity (RH) conditions remain a critical challenge for the successful introduction of fuel cells into mass markets. It was the goal of the team lead by Arkema, Inc. to address these shortages. Thus, this project addresses the following technical barriers from the fuel cells section of the Hydrogen Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan: (A) Durability (B) Cost Arkema’s approach consisted of using blends of polyvinylidenefluoride (PVDF) and proprietary sulfonated polyelectrolytes. In the traditional approach to polyelectrolytes for proton exchange membranes (PEM), all the required properties are “packaged” in one macromolecule. The properties of interest include proton conductivity, mechanical properties, durability, and water/gas transport. This is the case, for example, for perfluorosulfonic acid-containing (PFSA) membranes. However, the cost of these materials is high, largely due to the complexity and the number of steps involved in their synthesis. In addition, they suffer other shortcomings such as mediocre mechanical properties and insufficient durability for some applications. The strength and originality of Arkema’s approach lies in the decoupling of ion conductivity from the other requirements. Kynar® PVDF provides an exceptional combination of properties that make it ideally suited for a membrane matrix (Kynar® is a registered trademark of Arkema Inc.). It exhibits outstanding chemical resistance in highly oxidative and acidic environments. In work with a prior grant, a membrane known as M41 was developed by Arkema. M41 had many of the properties needed for a high performance PEM, but had a significant deficiency in conductivity at low RH. In the first phase of this work, the processing parameters of M41 were explored as a means to increase its proton

  9. Solid polymer electrolyte composite membrane comprising laser micromachined porous support

    DOEpatents

    Liu, Han; LaConti, Anthony B.; Mittelsteadt, Cortney K.; McCallum, Thomas J.

    2011-01-11

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a rigid, non-electrically-conducting support, the support preferably being a sheet of polyimide having a thickness of about 7.5 to 15 microns. The support has a plurality of cylindrical pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores, which preferably have a diameter of about 5 microns, are made by laser micromachining and preferably are arranged in a defined pattern, for example, with fewer pores located in areas of high membrane stress and more pores located in areas of low membrane stress. The pores are filled with a first solid polymer electrolyte, such as a perfluorosulfonic acid (PFSA) polymer. A second solid polymer electrolyte, which may be the same as or different than the first solid polymer electrolyte, may be deposited over the top and/or bottom of the first solid polymer electrolyte.

  10. Bipolar Membranes for Acid Base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Roddecha, Supacharee; Jorne, Jacob; Coughlan, Anna

    2011-03-01

    Rechargeable batteries can provide grid-scale electricity storage to match power generation with consumption and promote renewable energy sources. Flow batteries offer modular and flexible design, low cost per kWh and high efficiencies. A novel flow battery concept will be presented based on acid-base neutralization where protons (H+) and hydroxyl (OH-) ions react electrochemically to produce water. The large free energy of this highly reversible reaction can be stored chemically, and, upon discharge, can be harvested as usable electricity. The acid-base flow battery concept avoids the use of a sluggish oxygen electrode and utilizes the highly reversible hydrogen electrode, thus eliminating the need for expensive noble metal catalysts. The proposed flow battery is a hybrid of a battery and a fuel cell---hydrogen gas storing chemical energy is produced at one electrode and is immediately consumed at the other electrode. The two electrodes are exposed to low and high pH solutions, and these solutions are separated by a hybrid membrane containing a hybrid cation and anion exchange membrane (CEM/AEM). Membrane design will be discussed, along with ion-transport data for synthesized membranes.

  11. Lead Research and Development Activity for DOE's High Temperature, Low Relative Humidity Membrane Program (Topic 2)

    SciTech Connect

    James Fenton, PhD; Darlene Slattery, PhD; Nahid Mohajeri, PhD

    2012-09-05

    The Department of Energy’s High Temperature, Low Relative Humidity Membrane Program was begun in 2006 with the Florida Solar Energy Center (FSEC) as the lead organization. During the first three years of the program, FSEC was tasked with developing non-Nafion® proton exchange membranes with improved conductivity for fuel cells. Additionally, FSEC was responsible for developing protocols for the measurement of in-plane conductivity, providing conductivity measurements for the other funded teams, developing a method for through-plane conductivity and organizing and holding semiannual meetings of the High Temperature Membrane Working Group (HTMWG). The FSEC membrane research focused on the development of supported poly[perfluorosulfonic acid] (PFSA) – Teflon membranes and a hydrocarbon membrane, sulfonated poly(ether ether ketone). The fourth generation of the PFSA membrane (designated FSEC-4) came close to, but did not meet, the Go/No-Go milestone of 0.1 S/cm at 50% relative humidity at 120 °C. In-plane conductivity of membranes provided by the funded teams was measured and reported to the teams and DOE. Late in the third year of the program, DOE used this data and other factors to decide upon the teams to continue in the program. The teams that continued provided promising membranes to FSEC for development of membrane electrode assemblies (MEAs) that could be tested in an operating fuel cell. FSEC worked closely with each team to provide customized support. A logic flow chart was developed and discussed before MEA fabrication or any testing began. Of the five teams supported, by the end of the project, membranes from two of the teams were easily manufactured into MEAs and successfully characterized for performance. One of these teams exceeded performance targets, while the other requires further optimization. An additional team developed a membrane that shows great promise for significantly reducing membrane costs and increasing membrane lifetime.

  12. Recycling of used perfluorosulfonic acid membranes

    DOEpatents

    Grot, Stephen; Grot, Walther

    2007-08-14

    A method for recovering and recycling catalyst coated fuel cell membranes includes dissolving the used membranes in water and solvent, heating the dissolved membranes under pressure and separating the components. Active membranes are produced from the recycled materials.

  13. Radiation-Grafted Polymer Electrolyte Membranes for Water Electrolysis Cells: Evaluation of Key Membrane Properties.

    PubMed

    Albert, Albert; Barnett, Alejandro O; Thomassen, Magnus S; Schmidt, Thomas J; Gubler, Lorenz

    2015-10-14

    Radiation-grafted membranes can be considered an alternative to perfluorosulfonic acid (PFSA) membranes, such as Nafion, in a solid polymer electrolyte electrolyzer. Styrene, acrylonitrile, and 1,3-diisopropenylbenzene monomers are cografted into preirradiated 50 μm ethylene tetrafluoroethylene (ETFE) base film, followed by sulfonation to introduce proton exchange sites to the obtained grafted films. The incorporation of grafts throughout the thickness is demonstrated by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analysis of the membrane cross-sections. The membranes are analyzed in terms of grafting kinetics, ion-exchange capacity (IEC), and water uptake. The key properties of radiation-grafted membranes and Nafion, such as gas crossover, area resistance, and mechanical properties, are evaluated and compared. The plot of hydrogen crossover versus area resistance of the membranes results in a property map that indicates the target areas for membrane development for electrolyzer applications. Tensile tests are performed to assess the mechanical properties of the membranes. Finally, these three properties are combined to establish a figure of merit, which indicates that radiation-grafted membranes obtained in the present study are promising candidates with properties superior to those of Nafion membranes. A water electrolysis cell test is performed as proof of principle, including a comparison to a commercial membrane electrode assembly (MEA).

  14. Lactobacillus casei combats acid stress by maintaining cell membrane functionality.

    PubMed

    Wu, Chongde; Zhang, Juan; Wang, Miao; Du, Guocheng; Chen, Jian

    2012-07-01

    Lactobacillus casei strains have traditionally been recognized as probiotics and frequently used as adjunct culture in fermented dairy products where lactic acid stress is a frequently encountered environmental condition. We have investigated the effect of lactic acid stress on the cell membrane of L. casei Zhang [wild type (WT)] and its acid-resistant mutant Lbz-2. Both strains were grown under glucose-limiting conditions in chemostats; following challenge by low pH, the cell membrane stress responses were investigated. In response to acid stress, cell membrane fluidity decreased and its fatty acid composition changed to reduce the damage caused by lactic acid. Compared with the WT, the acid-resistant mutant exhibited numerous survival advantages, such as higher membrane fluidity, higher proportions of unsaturated fatty acids, and higher mean chain length. In addition, cell integrity analysis showed that the mutant maintained a more intact cellular structure and lower membrane permeability after environmental acidification. These results indicate that alteration in membrane fluidity, fatty acid distribution, and cell integrity are common mechanisms utilized by L. casei to withstand severe acidification and to reduce the deleterious effect of lactic acid on the cell membrane. This detailed comparison of cell membrane responses between the WT and mutant add to our knowledge of the acid stress adaptation and thus enable new strategies to be developed aimed at improving the industrial performance of this species under acid stress. PMID:22366811

  15. Impacts of hydrophilic colanic acid on bacterial attachment to microfiltration membranes and subsequent membrane biofouling.

    PubMed

    Yoshida, Keitaro; Tashiro, Yosuke; May, Thithiwat; Okabe, Satoshi

    2015-06-01

    In order to examine the interactions between physicochemical properties of specific extracellular polymeric substances (EPS) and membrane biofouling, we investigated the impacts of hydrophilic colanic acid, as a model extracellular polysaccharide component, on initial bacterial attachment to different microfiltration (MF) membranes and membrane biofouling by using Escherichia coli strains producing different amounts of colanic acid. In a newly designed microtiter plate assay, the bacterial attachment by an E. coli strain RcsF(+), which produces massive amounts of colanic acid, decreased only to a hydrophobic membrane because the colanic acid made cell surfaces more hydrophilic, resulting in low cell attachment to hydrophobic membranes. The bench-scale cross-flow filtration tests followed by filtration resistance measurement revealed that RcsF(+) caused severe irreversible membrane fouling (i.e., pore-clogging), whereas less extracellular polysaccharide-producing strains caused moderate but reversible fouling to all membranes used in this study. Further cross-flow filtration tests indicated that colanic acid liberated in the bulk phase could rapidly penetrate pre-accumulated biomass layers (i.e., biofilms) and then directly clogged membrane pores. These results indicate that colanic acid, a hydrophilic extracellular polysaccharide, and possible polysaccharides with similar characteristics with colanic acid are considered as a major cause of severe irreversible membrane fouling (i.e., pore-clogging) regardless of biofilm formation (dynamic membrane).

  16. Remodeling of Granulocyte Membrane Fatty Acids During Phagocytosis

    PubMed Central

    Smolen, James E.; Shohet, Stephen B.

    1974-01-01

    During phagocytosis, new phospholipid is synthesized from triglyceride fatty acid and may be utilized to form the membranes of phagocytic vesicles. In addition, hydrogen peroxide, which can peroxidize unsaturated fatty acids, is generated. Since both of these processes could change membrane fatty acid composition during the conversion of cytoplasmic granules and plasma membranes to phagosomes, the lipid compositions of these structures were examined. Phagocytic vesicles were prepared by density gradient centrifugation of polystyrene latex particles after phagocytosis. Granule and plasma membrane fractions were isolated by density gradient and differential centrifugation. Phospholipids and fatty acids were analyzed by thin-layer chromatography and gas-liquid chromatography. While whole cells, granules, plasma membranes, and phagosomes were all similar in phospholipid composition, phagosome fatty acids were significantly more saturated than those of the other fractions. This was primarily due to reduced oleic and arachidonic acids and increased palmitic acid in the phagocytic vesicle lipids. Plasma membrane was also more saturated in comparison to whole cells and granules. However, this difference was not sufficient to explain the marked comparative saturation of the phagosomes. The observed increase in fatty acid saturation in these lipids may have been induced by a combination of either peroxidative destruction of polyunsaturated fatty acids or phospholipase activity, coupled with reacylation mechanisms favoring saturated fatty acids. PMID:4812436

  17. Separation of certain carboxylic acids utilizing cation exchange membranes

    DOEpatents

    Chum, Helena L.; Sopher, David W.

    1984-01-01

    A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

  18. Separation of certain carboxylic acids utilizing cation exchange membranes

    DOEpatents

    Chum, H.L.; Sopher, D.W.

    1983-05-09

    A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

  19. Polyimide amic acid salts and polyimide membranes formed therefrom

    SciTech Connect

    Ding, Yong; Bikson, Benjamin; Nelson, Joyce Katz; Macheras, James Timothy

    2004-04-06

    The invention relates to preparation and uses of novel polymeric materials, polyimide amic acid salts (PIAAS). The use of these materials for the fabrication of fluid separation membranes is further disclosed.

  20. Vapour and acid components separation from gases by membranes principles and engineering approach to membranes development

    NASA Astrophysics Data System (ADS)

    Kagramanov, G. G.; Storojuk, I. P.; Farnosova, E. N.

    2016-09-01

    The modern commercially available polymer membranes and membrane modules for purification of gases, containing acid components, simultaneously with dehumidification of treated gas streams, were developed and commercialized in the very end of XXth century. The membranes basic properties - selectivity (separation factor) and permeation flow rates - are relatively far from satisfying the growing and modern-scale industrial need in purification technologies and corresponding equipments. The attempt to formulate the basic principles, scientific and engineering approaches to the development of prospective membranes for the purification of gases, especially such as natural and oil gases, from acid components, simultaneously with drying them, was being made. For this purpose the influence of various factors - polymer nature, membrane type, structure, geometrical and mass-transfer characteristics, etc. - were studied and analyzed in order to formulate the basic principles and demands for development of membranes, capable to withstand successfully the sever conditions of exploitation.

  1. BASELINE MEMBRANE SELECTION AND CHARACTERIZATION FOR AN SDE

    SciTech Connect

    Colon-Mercado, H; David Hobbs, D

    2007-04-03

    Thermochemical processes are being developed to provide global-scale quantities of hydrogen. A variant on sulfur-based thermochemical cycles is the Hybrid Sulfur (HyS) Process which uses a sulfur dioxide depolarized electrolyzer (SDE) to produce the hydrogen. In FY05 and FY06, testing at the Savannah River National Laboratory (SRNL) explored a low temperature fuel cell design concept for the SDE. The advantages of this design concept include high electrochemical efficiency and small footprint that are crucial for successful implementation on a commercial scale. A key component of the SDE is the ion conductive membrane through which protons produced at anode migrate to the cathode and react to produce hydrogen. An ideal membrane for the SDE should have both low ionic resistivity and low sulfur dioxide transport. These features allow the electrolyzer to perform at high currents with low potentials, along with preventing contamination of both the hydrogen output and poisoning of the catalysts involved. Another key component is the electrocatalyst material used for the anode and cathode. Good electrocatalysts should be chemically stable and have a low overpotential for the desired electrochemical reactions. This report summarizes results from activities to evaluate commercial and experimental membranes for the SDE. Several different types of commercially-available membranes were analyzed for sulfur dioxide transport as a function of acid strength including perfluorinated sulfonic acid (PFSA), sulfonated poly-etherketone-ketone, and poly-benzimidazole (PBI) membranes. Experimental membranes from the sulfonated diels-alder polyphenylenes (SDAPP) and modified Nafion{reg_sign} 117 were evaluated for SO{sub 2} transport as well. These membranes exhibited reduced transport coefficient for SO{sub 2} transport without the loss in ionic conductivity. The use of Nafion{reg_sign} with EW 1100 is recommended for the present SDE testing due to the limited data regarding chemical

  2. Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species.

    PubMed

    Carmona-Salazar, Laura; El Hafidi, Mohammed; Gutiérrez-Nájera, Nora; Noyola-Martínez, Liliana; González-Solís, Ariadna; Gavilanes-Ruíz, Marina

    2015-01-01

    It is essential to establish the composition of the plant plasma membrane in order to understand its organization and behavior under continually changing environments. Knowledge of the lipid phase, in particular the fatty acid (FA) complex repertoire, is important since FAs determine many of the physical-chemical membrane properties. FAs are constituents of the membrane glycerolipid and sphingolipid backbones and can also be linked to some sterols. In addition, FAs are components of complex lipids that can constitute membrane micro-domains, and the use of detergent-resistant membranes is a common approach to study their composition. The diversity and cellular allocation of the membrane lipids containing FAs are very diverse and the approaches to analyze them provide only general information. In this work, a detailed FA analysis was performed using highly purified plasma membranes from bean leaves and germinating maize embryos and their respective detergent-resistant membrane preparations. The analyses showed the presence of a significant amount of very long chain FAs (containing 28C, 30C and 32C), in both plasma membrane preparations from bean and maize, that have not been previously reported. Herein is demonstrated that a significant enrichment of very long chain saturated FAs and saturated FAs can occur in detergent-resistant membrane preparations, as compared to the plasma membranes from both plant species. Considering that a thorough analysis of FAs is rarely performed in purified plasma membranes and detergent-resistant membranes, this work provides qualitative and quantitative evidence on the contributions of the length and saturation of FAs to the organization of the plant plasma membrane and detergent-resistant membranes.

  3. Photolabeling of brain membrane proteins by lysergic acid diethylamide

    SciTech Connect

    Mahon, A.C.; Hartig, P.R.

    1982-04-05

    /sup 3/H-Lysergic acid diethylamide (/sup 3/H-LSD) is irreversibly incorporated into bovine caudate membranes during ultraviolet light illumination. The incorporated radioligand apparently forms a covalent bond with a sub-population of the membrane proteins. Although the photolabeling pattern differs significantly from the Coomassie blue staining pattern on SDS gels, the photolabeling is apparently not specific for LSD binding sites associated with neurotransmitter receptors. /sup 3/H-LSD photolabeling can occur during prolonged exposure of membrane samples to room lighting and thus may introduce artifacts into receptor binding assays.

  4. Flocculation and Membrane Binding of Outer Membrane Protein F, Porin, at Acidic pH

    NASA Astrophysics Data System (ADS)

    Suzuki, Keiko; Nakae, Taiji; Mitaku, Shigeki

    1998-04-01

    Outer membrane protein F (OmpF), porin, of Escherichia coli is an intrinsic membrane protein made of a β-sheet barrel, the amino acid sequence being as hydrophilic as many soluble proteins in spite of its location in the hydrophobic region of membrane. The binding of porin molecules with a lipid membrane and the flocculation of the protein were studied at various pH, using the combination of centrifugation and intrinsic fluorescence measurements. The binding of porin with the lipid membrane occurred in the pH range below 7, whereas the flocculation of porin in the absence of the membrane was observed only at pH below 5. Porin molecules in the pH range between 5 and 7 were stable as a colloid but spontaneously bound with the lipid membrane soon after the addition of lipid vesicles. The possible mechanism of the structural formation of porin in the outer membrane was discussed based on the pH dependence of the membrane binding ability of this protein.

  5. Erythrocyte membrane fatty acids in multiple myeloma patients.

    PubMed

    Jurczyszyn, Artur; Czepiel, Jacek; Gdula-Argasińska, Joanna; Czapkiewicz, Anna; Biesiada, Grażyna; Dróżdż, Mirosław; Perucki, William; Castillo, Jorge J

    2014-10-01

    Mounting data show that fatty acids (FA) and fatty acid synthase (FAS) function could be potential targets for multiple myeloma (MM) therapy. Our study aimed at comparing the FA composition of erythrocyte membranes of MM patients and healthy controls. MM patients had higher saturated FA and n-6 polyunsaturated FA (PUFA) and lower monounsaturated, n-3 PUFA and trans-FA indices than controls. The n-3/n-6 PUFA ratio was lower in MM patients and there was distinct clustering of variants of individual FA in MM patients. The FA content of erythrocyte membrane could serve as a diagnostic and/or predictive biomarker in MM.

  6. Recovery of volatile fatty acids via membrane contactor using flat membranes: experimental and theoretical analysis.

    PubMed

    Tugtas, Adile Evren

    2014-07-01

    Volatile fatty acid (VFA) separation from synthetic VFA solutions and leachate was investigated via the use of a membrane contactor. NaOH was used as a stripping solution to provide constant concentration gradient of VFAs in both sides of a membrane. Mass flux (12.23 g/m(2)h) and selectivity (1.599) observed for acetic acid were significantly higher than those reported in the literature and were observed at feed pH of 3.0, flow rate of 31.5 ± 0.9 mL/min, and stripping solution concentration of 1.0 N. This study revealed that the flow rate, stripping solution strength, and feed pH affect the mass transfer of VFAs through the PTFE membrane. Acetic and propionic acid separation performances observed in the present study provided a cost effective and environmental alternative due to elimination of the use of extractants.

  7. Evaluation of the effect of impregnated platinum on PFSA degradation for PEM fuel cells.

    SciTech Connect

    Rodgers, Marianne; Pearman, Benjamin P; Bonville, Leonard J.; Cullen, David A; Mohajeri, Nahid; Slattery, Darlene

    2013-01-01

    One of the main sources of membrane degradation in fuel cells is attack by radicals formed wherever Pt, H2, and O2 are present. The effect of Pt precipitated in the membrane is under debate. Although Pt can provide another site for radical formation, it can also scavenge hydrogen peroxide and radicals in the membrane and improve durability. In this work, the effects of Pt particles within the membrane are evaluated and related to membrane degradation. Membranes were ex situ impregnated with 0, 10, 30, and 50 mol% Pt and then tested for 100 h in a fuel cell, at 90 C/100% relative humidity. The highest degradation was observed with the membranes containing 10 mol% Pt, with fluoride emissions of the same magnitude as those of catalyst coated membranes containing Pt/C. Membranes containing 0, 30, and 50 mol% Pt resulted in very low fluoride emission. The high degradation in the 10 mol% membrane was attributed to the low density of platinum particles, which allows generated radicals to attack the membrane before being deactivated. In the 30 mol% and 50 mol% membranes, where the platinum particles were denser, the generated radicals became deactivated on neighboring particles before they attacked the membrane.

  8. Nucleic acid-lipid membrane interactions studied by DSC.

    PubMed

    Giatrellis, Sarantis; Nounesis, George

    2011-01-01

    The interactions of nucleic acids with lipid membranes are of great importance for biological mechanisms as well as for biotechnological applications in gene delivery and drug carriers. The optimization of liposomal vectors for clinical use is absolutely dependent upon the formation mechanisms, the morphology, and the molecular organization of the lipoplexes, that is, the complexes of lipid membranes with DNA. Differential scanning calorimetry (DSC) has emerged as an efficient and relatively easy-to-operate experimental technique that can straightforwardly provide data related to the thermodynamics and the kinetics of the DNA-lipid complexation and especially to the lipid organization and phase transitions within the membrane. In this review, we summarize DSC studies considering nucleic acid-membrane systems, accentuating DSC capabilities, and data analysis. Published work involving cationic, anionic, and zwitterionic lipids as well as lipid mixtures interacting with RNA and DNA of different sizes and conformations are included. It is shown that despite limitations, issues such as DNA- or RNA-induced phase separation and microdomain lipid segregation, liposomal aggregation and fusion, alterations of the lipid long-range molecular order, as well as membrane-induced structural changes of the nucleic acids can be efficiently treated by systematic high-sensitivity DSC studies.

  9. Conductivity Measurements of Synthesized Heteropoly Acid Membranes for Proton Exchange Membrane Fuel Cells

    SciTech Connect

    Record, K.A.; Haley, B.T.; Turner, J.

    2006-01-01

    Fuel cell technology is receiving attention due to its potential to be a pollution free method of electricity production when using renewably produced hydrogen as fuel. In a Proton Exchange Membrane (PEM) fuel cell H2 and O2 react at separate electrodes, producing electricity, thermal energy, and water. A key component of the PEM fuel cell is the membrane that separates the electrodes. DuPont’s Nafion® is the most commonly used membrane in PEM fuel cells; however, fuel cell dehydration at temperatures near 100°C, resulting in poor conductivity, is a major hindrance to fuel cell performance. Recent studies incorporating heteropoly acids (HPAs) into membranes have shown an increase in conductivity and thus improvement in performance. HPAs are inorganic materials with known high proton conductivities. The primary objective of this work is to measure the conductivity of Nafion, X-Ionomer membranes, and National Renewable Energy Laboratory (NREL) Developed Membranes that are doped with different HPAs at different concentrations. Four-point conductivity measurements using a third generation BekkTech conductivity test cell are used to determine membrane conductivity. The effect of multiple temperature and humidification levels is also examined. While the classic commercial membrane, Nafion, has a conductivity of approximately 0.10 S/cm, measurements for membranes in this study range from 0.0030 – 0.58 S/cm, depending on membrane type, structure of the HPA, and the relative humidity. In general, the X-ionomer with H6P2W21O71 HPA gave the highest conductivity and the Nafion with the 12-phosphotungstic (PW12) HPA gave the lowest. The NREL composite membranes had conductivities on the order of 0.0013 – 0.025 S/cm.

  10. Acid gas scrubbing by composite solvent-swollen membranes

    DOEpatents

    Matson, Stephen L.; Lee, Eric K. L.; Friesen, Dwayne T.; Kelly, Donald J.

    1988-01-01

    A composite immobilized liquid membrane suitable for acid gas scrubbing is disclosed. The membrane is a solvent-swollen polymer and a microporous polymeric support, the solvent being selected from a class of highly polar solvents containing at least one atom selected from nitrogen, oxygen, phosphorous and sulfur, and having a boiling point of at least 100.degree. C. and a solubility parameter of from about 7.5 to about 13.5 (cal/cm.sup.3 -atm).sup.1/2. Such solvents are homogeneously distributed through the solvent-swollen polymer from 20% to 95% by weight. Also disclosed are methods of acid gas scrubbing of high- and low-Btu gas effluents with such solvent-swollen membranes.

  11. Acid gas scrubbing by composite solvent-swollen membranes

    DOEpatents

    Matson, S.L.; Lee, E.K.L.; Friesen, D.T.; Kelly, D.J.

    1988-04-12

    A composite immobilized liquid membrane suitable for acid gas scrubbing is disclosed. The membrane is a solvent-swollen polymer and a microporous polymeric support, the solvent being selected from a class of highly polar solvents containing at least one atom selected from nitrogen, oxygen, phosphorus and sulfur, and having a boiling point of at least 100 C and a solubility parameter of from about 7.5 to about 13.5 (cal/cm[sup 3]-atm)[sup 1/2]. Such solvents are homogeneously distributed through the solvent-swollen polymer from 20% to 95% by weight. Also disclosed are methods of acid gas scrubbing of high- and low-Btu gas effluents with such solvent-swollen membranes. 3 figs.

  12. Hydrofluoric and nitric acid transport through lipid bilayer membranes.

    PubMed

    Gutknecht, J; Walter, A

    1981-06-01

    Hydrofluoric and nitric acid transport through lipid bilayer membranes were studied by a combination of electrical conductance and pH electrode techniques. Transport occurs primarily by nonionic diffusion of molecular HF and HNO3. Membrane permeabilities to HF and HNO3 ranged from 10(-4) to 10(-3) cm . s-1, five to seven orders of magnitude higher than the permeabilities to NO-3, F- and H+. Our results are consistent with the hypothesis that F- transport through biological membranes occurs mainly by nonionic diffusion of HF. Our results also suggest that of the two principal components of 'acid rain', HNO3 may be more toxic than H2SO4.

  13. Acid tolerance, proton permeabilities, and membrane ATPases of oral streptococci.

    PubMed Central

    Bender, G R; Sutton, S V; Marquis, R E

    1986-01-01

    Differences in acid tolerance among representative oral streptococci were found to be related more closely to the dynamic permeabilities of the bacteria to protons than to differences in the sensitivities of cell membranes to gross damage caused by environmental acidification. For Streptococcus mutans GS-5, Streptococcus sanguis NCTC 10904, and Streptococcus salivarius ATCC 13419, gross membrane damage, indicated by the release of magnesium from whole cells, occurred at pH values below about 4 and was rapid and extensive at pH values of about 3 or less. A more aciduric, lactic acid bacterium, Lactobacillus casei ATCC 4646, was more resistant to environmental acidification, and gross membrane damage was evident only at pH values below 3. Assessments of the movements of protons into S. mutans cells after an acid pulse at various pH values indicated that permeability to protons was minimal at a pH value of about 5, at which the average half time for pH equilibration across the cell membrane was about 12 min. The corresponding values for the less aciduric organism S. sanguis were pH 7 and 8.2 min, and the values for the intermediate organism S. salivarius were pH 6 and 6.6 min. The ATPase inhibitor dicyclohexylcarbodiimide acted to increase markedly the permeability of each organism to protons, and this action indicated that permeability involved not only the passive inflow of protons but also active outflow through the proton-translocating membrane ATPase. Membranes were isolated from each of the bacteria, and pH profiles for ATPase activities indicated pH optima of about 7.5, 7.0, 6.0, and 5.0 for S. sanguis, S. salivarius, S. mutans, and L. casei, respectively. Thus, the pH profiles for the enzymes reflected the acid tolerances of the bacteria and the permeabilities of whole cells to protons. PMID:3015800

  14. Carboxylic Acids Plasma Membrane Transporters in Saccharomyces cerevisiae.

    PubMed

    Casal, Margarida; Queirós, Odília; Talaia, Gabriel; Ribas, David; Paiva, Sandra

    2016-01-01

    This chapter covers the functionally characterized plasma membrane carboxylic acids transporters Jen1, Ady2, Fps1 and Pdr12 in the yeast Saccharomyces cerevisiae, addressing also their homologues in other microorganisms, as filamentous fungi and bacteria. Carboxylic acids can either be transported into the cells, to be used as nutrients, or extruded in response to acid stress conditions. The secondary active transporters Jen1 and Ady2 can mediate the uptake of the anionic form of these substrates by a H(+)-symport mechanism. The undissociated form of carboxylic acids is lipid-soluble, crossing the plasma membrane by simple diffusion. Furthermore, acetic acid can also be transported by facilitated diffusion via Fps1 channel. At the cytoplasmic physiological pH, the anionic form of the acid prevails and it can be exported by the Pdr12 pump. This review will highlight the mechanisms involving carboxylic acids transporters, and the way they operate according to the yeast cell response to environmental changes, as carbon source availability, extracellular pH and acid stress conditions.

  15. Nucleic acid-lipid membrane interactions studied by DSC

    PubMed Central

    Giatrellis, Sarantis; Nounesis, George

    2011-01-01

    The interactions of nucleic acids with lipid membranes are of great importance for biological mechanisms as well as for biotechnological applications in gene delivery and drug carriers. The optimization of liposomal vectors for clinical use is absolutely dependent upon the formation mechanisms, the morphology, and the molecular organization of the lipoplexes, that is, the complexes of lipid membranes with DNA. Differential scanning calorimetry (DSC) has emerged as an efficient and relatively easy-to-operate experimental technique that can straightforwardly provide data related to the thermodynamics and the kinetics of the DNA—lipid complexation and especially to the lipid organization and phase transitions within the membrane. In this review, we summarize DSC studies considering nucleic acid—membrane systems, accentuating DSC capabilities, and data analysis. Published work involving cationic, anionic, and zwitterionic lipids as well as lipid mixtures interacting with RNA and DNA of different sizes and conformations are included. It is shown that despite limitations, issues such as DNA- or RNA-induced phase separation and microdomain lipid segregation, liposomal aggregation and fusion, alterations of the lipid long-range molecular order, as well as membrane-induced structural changes of the nucleic acids can be efficiently treated by systematic high-sensitivity DSC studies. PMID:21430956

  16. Swelling assisted photografting of itaconic acid onto sodium alginate membranes

    NASA Astrophysics Data System (ADS)

    Taşkın, Gülşen; Şanlı, Oya; Asman, Gülsen

    2011-09-01

    Grafting of itaconic acid (IA) was achieved onto sodium alginate (NaAlg) membranes by using UV-radiation. Process was performed under nitrogen atmosphere and benzophenone (BP) was used as a photoinitiator. Membranes were preswelled before the polymerization process and ethanol was determined as the best swelling agent among the studied solvents. The effect of polymerization time, initiator and monomer concentrations on the grafting efficiency were investigated. The best conditions for optimum grafting were obtained with IA concentration of 1.0 M, a BP concentration of 0.1 M and a reaction time of 4 h at 25 °C. Under these conditions grafting efficiency for NaAlg-g-IA membranes was found to be 14% (w/w). To obtain further increase in grafting efficiency membranes were also preswelled in IA and BP solutions and polymerization was carried out at different temperatures after UV polymerization. Grafted membranes were characterized by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Effect of grafting on membrane properties such as intrinsic viscosity and swelling percentage were also determined.

  17. NHI-Acid Concentration Membranes -- Membrane Recommendations for the S-I Cycle

    SciTech Connect

    Frederick F Stewart

    2007-03-01

    Scope: The purpose of this draft report is to make recommendations concerning the applicability of specific membrane materials for acid concentration processes to the Sulfur-Iodine (S-I) thermochemical cycle integrated laboratory scale (ILS) demonstration. Introduction Acid concentration membrane processes have been studied for possible inclusion in the Sulfur-Iodine integrated laboratory scale (S-I ILS) demonstration. The need for this technology is driven by the chemical processes required for economical water splitting using the S-I cycle. Of the chemical processes inherent to the S-I cycle that have been identified as targets for deployment of membrane technology, three have been studied during the past three fiscal years as a part of the DOE Nuclear Hydrogen Initiative. First, the ability to concentrate hydriodic acid (HI) and iodine mixtures was sought as a method for aiding in the isolation of HI away from water and iodine. Isolated HI would then be delivered to the HI decomposition process for liberation of product hydrogen. Second, an extension of this technology to sulfuric acid was proposed to benefit sulfuric acid decomposition recycle. Third, decomposition of HI to form hydrogen is equilibrium limited. Removal of hydrogen, utilizing Le Chatelier’s principle, will increase to overall conversion and thus increasing the efficiency of the S-I cycle.

  18. Smoking and red blood cell phospholipid membrane fatty acids.

    PubMed

    Murff, H J; Tindle, H A; Shrubsole, M J; Cai, Q; Smalley, W; Milne, G L; Swift, L L; Ness, R M; Zheng, W

    2016-09-01

    Smoking is associated with lower n-3 long chain polyunsaturated fatty acids (LCPUFA) concentrations; however, limited studies have accounted for dietary PUFA intake or whether tobacco dose or smoking duration influences this association. We measured red blood cell phospholipid (RBC) membrane concentrations of fatty acids in 126 current smokers, 311 former smokers, and 461 never smokers using gas liquid chromatography and tandem mass spectrometry. Smokers had lower RBC membrane percentages of total n-3 LCPUFAs compared to former smokers or never smokers (median percent: 5.46, [interquartile range (IQR) 4.52, 6.28] versus 6.39; [IQR: 5.18, 7.85] versus 6.59; [IQR 5.34, 8.01]) (p<0.001) and this association remained after adjusting for dietary PUFA intake. Duration of smoking and cigarettes per day were not associated with RBC membrane n-3 LCPUFA differences. Smoking is associated with lower n-3 LCPUFA RBC membrane percentages and this association was not influenced by diet or smoking dose or duration. PMID:27637337

  19. Permeability of membranes to amino acids and modified amino acids: mechanisms involved in translocation

    NASA Technical Reports Server (NTRS)

    Chakrabarti, A. C.; Deamer, D. W. (Principal Investigator); Miller, S. L. (Principal Investigator)

    1994-01-01

    The amino acid permeability of membranes is of interest because they are one of the key solutes involved in cell function. Membrane permeability coefficients (P) for amino acid classes, including neutral, polar, hydrophobic, and charged species, have been measured and compared using a variety of techniques. Decreasing lipid chain length increased permeability slightly (5-fold), while variations in pH had only minor effects on the permeability coefficients of the amino acids tested in liposomes. Increasing the membrane surface charge increased the permeability of amino acids of the opposite charge, while increasing the cholesterol content decreased membrane permeability. The permeability coefficients for most amino acids tested were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium (approximately 10(-12)-10(-13) cm s-1). This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. Hydrophobic amino acids were 10(2) more permeable than the hydrophilic forms, reflecting their increased partition coefficient values. External pH had dramatic effects on the permeation rates for the modified amino acid lysine methyl ester in response to transmembrane pH gradients. It was established that lysine methyl ester and other modified short peptides permeate rapidly (P = 10(-2) cm s-1) as neutral (deprotonated) molecules. It was also shown that charge distributions dramatically alter permeation rates for modified di-peptides. These results may relate to the movement of peptides through membranes during protein translocation and to the origin of cellular membrane transport on the early Earth.

  20. α-Lactalbumin:Oleic Acid Complex Spontaneously Delivers Oleic Acid to Artificial and Erythrocyte Membranes.

    PubMed

    Wen, Hanzhen; Strømland, Øyvind; Halskau, Øyvind

    2015-09-25

    Human α-lactalbumin made lethal to tumor cells (HAMLET) is a tumoricidal complex consisting of human α-lactalbumin and multiple oleic acids (OAs). OA has been shown to play a key role in the activity of HAMLET and its related complexes, generally known as protein-fatty acid (PFA) complexes. In contrast to what is known about the fate of the protein component of such complexes, information about what happens to OA during their action is still lacking. We monitored the membrane, OA and protein components of bovine α-lactalbumin complexed with OA (BLAOA; a HAMLET-like substance) and how they associate with each other. Using ultracentrifugation, we found that the OA and lipid components follow each other closely. We then firmly identify a transfer of OA from BLAOA to both artificial and erythrocyte membranes, indicating that natural cells respond similarly to BLAOA treatment as artificial membranes. Uncomplexed OA is unable to similarly affect membranes at the conditions tested, even at elevated concentrations. Thus, BLAOA can spontaneously transfer OA to a lipid membrane. After the interaction with the membrane, the protein is likely to have lost most or all of its OA. We suggest a mechanism for passive import of mainly uncomplexed protein into cells, using existing models for OA's effect on membranes. Our results are consistent with a membrane destabilization mediated predominantly by OA insertion being a significant contribution to PFA cytotoxicity.

  1. Effects of atrazine on Ochrobactrum anthropi membrane fatty acids.

    PubMed Central

    Laura, D; De Socio, G; Frassanito, R; Rotilio, D

    1996-01-01

    Ochrobactrum anthropi is a gram-negative bacillus recognized as a human opportunist pathogen isolated in clinical specimens and not of clinical significance. We report a new aspect of this bacterium, that it has been isolated from activated sludge. In fact, it is able to grow on atrazine (2-chloro-4-ethylamino-6-isopropyl-amine-s-triazine) by utilizing it as the only source of carbon. Our results show that atrazine (0.03 g/liter) causes a dramatical increase in the degree of saturation of membrane fatty acids. Analysis and identification of bacterial fatty acids were performed by gas chromatography and gas chromatography-mass spectrometry techniques. PMID:8779602

  2. Anacardic acid-mediated changes in membrane potential and pH gradient across liposomal membranes.

    PubMed

    Toyomizu, Masaaki; Okamoto, Katsuyuki; Akiba, Yukio; Nakatsu, Tetsuo; Konishi, Tetsuya

    2002-01-01

    We have previously shown that anacardic acid has an uncoupling effect on oxidative phosphorylation in rat liver mitochondria using succinate as a substrate (Life Sci. 66 (2000) 229-234). In the present study, for clarification of the physicochemical characteristics of anacardic acid, we used a cyanine dye (DiS-C3(5)) and 9-aminoacridine (9-AA) to determine changes of membrane potential (DeltaPsi) and pH difference (DeltapH), respectively, in a liposome suspension in response to the addition of anacardic acid to the suspension. The anacardic acid quenched DiS-C3(5) fluorescence at concentrations higher than 300 nM, with the degree of quenching being dependent on the log concentration of the acid. Furthermore, the K(+) diffusion potential generated by the addition of valinomycin to the suspension decreased for each increase in anacardic acid concentration used over 300 nM, but the sum of the anacardic acid- and valinomycin-mediated quenching was additively increasing. This indicates that the anacardic acid-mediated quenching was not due simply to increments in the K(+) permeability of the membrane. Addition of anacardic acid in the micromolar range to the liposomes with DeltaPsi formed by valinomycin-K(+) did not significantly alter 9-AA fluorescence, but unexpectedly dissipated DeltaPsi. The DeltaPsi preformed by valinomycin-K(+) decreased gradually following the addition of increasing concentrations of anacardic acid. The DeltaPsi dissipation rate was dependent on the pre-existing magnitude of DeltaPsi, and was correlated with the logarithmic concentration of anacardic acid. Furthermore, the initial rate of DeltapH dissipation increased with logarithmic increases in anacardic acid concentration. These results provide the evidence for a unique function of anacardic acid, dissimilar to carbonylcyanide p-trifluoromethoxyphenylhydrazone or valinomycin, in that anacardic acid behaves as both an electrogenic (negative) charge carrier driven by DeltaPsi, and a 'proton

  3. Influences of acid-base property of membrane on interfacial interactions related with membrane fouling in a membrane bioreactor based on thermodynamic assessment.

    PubMed

    Zhao, Leihong; Qu, Xiaolu; Zhang, Meijia; Lin, Hongjun; Zhou, Xiaoling; Liao, Bao-Qiang; Mei, Rongwu; Hong, Huachang

    2016-08-01

    Failure of membrane hydrophobicity in predicting membrane fouling requires a more reliable indicator. In this study, influences of membrane acid base (AB) property on interfacial interactions in two different interaction scenarios in a submerged membrane bioreactor (MBR) were studied according to thermodynamic approaches. It was found that both the polyvinylidene fluoride (PVDF) membrane and foulant samples in the MBR had relatively high electron donor (γ(-)) component and low electron acceptor (γ(+)) component. For both of interaction scenarios, AB interaction was the major component of the total interaction. The results showed that, the total interaction monotonically decreased with membrane γ(-), while was marginally affected by membrane γ(+), suggesting that γ(-) could act as a reliable indicator for membrane fouling prediction. This study suggested that membrane modification for fouling mitigation should orient to improving membrane surface γ(-) component rather than hydrophilicity. PMID:27155263

  4. Solid polymer electrolyte composite membrane comprising plasma etched porous support

    DOEpatents

    Liu, Han; LaConti, Anthony B.

    2010-10-05

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a rigid, non-electrically-conducting support, the support preferably being a sheet of polyimide having a thickness of about 7.5 to 15 microns. The support has a plurality of cylindrical pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores, which preferably have a diameter of about 0.1 to 5 microns, are made by plasma etching and preferably are arranged in a defined pattern, for example, with fewer pores located in areas of high membrane stress and more pores located in areas of low membrane stress. The pores are filled with a first solid polymer electrolyte, such as a perfluorosulfonic acid (PFSA) polymer. A second solid polymer electrolyte, which may be the same as or different than the first solid polymer electrolyte, may be deposited over the top and/or bottom of the first solid polymer electrolyte.

  5. Hollow fiber gas-liquid membrane contactors for acid gas capture: a review.

    PubMed

    Mansourizadeh, A; Ismail, A F

    2009-11-15

    Membrane contactors using microporous membranes for acid gas removal have been extensively reviewed and discussed. The microporous membrane acts as a fixed interface between the gas and the liquid phase without dispersing one phase into another that offers a flexible modular and energy efficient device. The gas absorption process can offer a high selectivity and a high driving force for transport even at low concentrations. Using hollow fiber gas-liquid membrane contactors is a promising alternative to conventional gas absorption systems for acid gas capture from gas streams. Important aspects of membrane contactor as an efficient energy devise for acid gas removal including liquid absorbents, membrane characteristics, combination of membrane and absorbent, mass transfer, membrane modules, model development, advantages and disadvantages were critically discussed. In addition, current status and future potential in research and development of gas-liquid membrane contactors for acid gas removal were also briefly discussed.

  6. Colorimetric determination of phosphoric acid leakage for phosphoric acid-doped polybenzimidazole membrane fuel cell applications

    NASA Astrophysics Data System (ADS)

    Jeong, Yeon Hun; Jung, Ju Hae; Choi, Euiji; Han, Seungyoon; Begley, Alina Irene; Yoo, Sung Jong; Jang, Jong Hyun; Kim, Hyoung-Juhn; Nam, Suk Woo; Lee, Kwan-Young; Kim, Jin Young

    2015-12-01

    A simple and precise colorimetric method for analyzing phosphoric acid leakage in phosphoric acid-doped polybenzimidazole membrane fuel cells is described. The developed method is based on the colorimetric determination from a rapid formation of molybdenum blue color by the reduction reaction of molybdate ions in the presence of phosphoric acid in the acidic medium. The color is stable up to a few months and can be used for the sensitive and accurate detection of phosphoric acid electrolyte which is discharged from the fuel cell during operation. Tests with a wide concentration range of phosphate compounds showed that it permits determination of phosphoric acid up to nanogram quantities. The developed detection method assists monitoring the phosphoric acid contents and developing stable operation strategies of fuel cells.

  7. Simulation of ionomer membrane fatigue under mechanical and hygrothermal loading conditions

    NASA Astrophysics Data System (ADS)

    Khorasany, Ramin M. H.; Kjeang, Erik; Wang, G. G.; Rajapakse, R. K. N. D.

    2015-04-01

    Understanding the fatigue lifetime of common perfluorosulfonic acid (PFSA) ionomer membranes under fluctuating hygrothermal conditions is essential for the development of durable fuel cell technologies. For this purpose, a finite element based fatigue lifetime prediction model is developed based on an elastic-plastic constitutive model combined with a Smith-Watson-Topper (SWT) fatigue formulation. The model is validated against previously reported experimental results for a membrane under cyclic mechanical loadings. The validated model is then utilized to investigate the membrane fatigue lifetime in ex-situ applications under cyclic humidity and temperature conditions. The simulations suggest that the membrane fatigue lifetime is shorter under fluctuating humidity loadings than for temperature loadings. Additionally, the membrane fatigue lifetime is found to be more sensitive to the amplitude of the strain oscillations than to the mean strain under hygrothermal cycling. Most notably, the model predicts that simultaneous humidity and temperature cycling can exacerbate the fatigue process and reduce the fatigue lifetime by several orders of magnitude compared to isolated humidity or temperature cycling. The combination of measured mechanical fatigue data and the present numerical model provides a useful toolkit for analysis of membrane fatigue due to hygrothermal variations, which can be costly and time-consuming when addressed experimentally.

  8. Lactic acid fermentation in cell-recycle membrane bioreactor.

    PubMed

    Choudhury, B; Swaminathan, T

    2006-02-01

    Traditional lactic acid fermentation suffers from low productivity and low product purity. Cell-recycle fermentation has become one of the methods to obtain high cell density, which results in higher productivity. Lactic acid fermentation was investigated in a cell-recycle membrane bioreactor at higher substrate concentrations of 100 and 120 g/dm3. A maximum cell density of 145 g/dm3 and a maximum productivity of 34 g/(dm3.h) were achieved in cell-recycle fermentation. In spite of complete consumption of substrate, there was a continuous increase in cell density in cell-recycle fermentation. Control of cell density in cell-recycle fermentation was attempted by cell bleeding and reduction in yeast extract concentration.

  9. Gluconic acid production in bioreactor with immobilized glucose oxidase plus catalase on polymer membrane adjacent to anion-exchange membrane.

    PubMed

    Godjevargova, Tzonka; Dayal, Rajeshwar; Turmanova, Sevdalina

    2004-10-20

    Gluconic acid was obtained in the permeate side of the bioreactor with glucose oxidase (GOD) immobilized onto anion-exchange membrane (AEM) of low-density polyethylene grafted with 4-vinylpiridine. The electric resistance of the anion-exchange membranes was increased after the enzyme immobilization on the membrane. The gluconic acid productions were relatively low with the GOD immobilized by any method on the AEM. To increase the enzyme reaction efficiency, GOD was immobilized on membrane of AN copolymer (PAN) adjacent to an anion-exchange membrane in bioreactor. Uses of anion-exchange membrane led to selective removal of the gluconic acid from the glucose solution and reduce the gluconic acid inhibition. The amount of gluconic acid obtained in the permeate side of the bioreactor with the GOD immobilized on the PAN membrane adjacent to the AEM under electrodialysis was about 30 times higher than that obtained with enzyme directly bound to the AEM. The optimal substrate concentration in the feed side was found to be about 1 g/l. Further experiments were carried out with the co-immobilized GOD plus Catalase (CAT) on the PAN membrane adjacent to the AEM to improve the efficiency of the immobilize system. The yield of this process was at least 95%. The storage stability of the co-immobilized GOD and CAT was studied (lost 20% of initial activity for 90 d). The results obtained clearly showed the higher potential of the dual membrane bioreactor with GOD plus CAT bound to ultrafiltration polymer membrane adjacent to the AEM. Storage stability of GOD activity in GOD plus CAT immobilized on PAN//AEM membranes and on AEM.

  10. Sialic Acid Glycobiology Unveils Trypanosoma cruzi Trypomastigote Membrane Physiology

    PubMed Central

    Lantos, Andrés B.; Carlevaro, Giannina; Araoz, Beatriz; Ruiz Diaz, Pablo; Camara, María de los Milagros; Buscaglia, Carlos A.; Bossi, Mariano; Yu, Hai; Chen, Xi; Bertozzi, Carolyn R.; Mucci, Juan; Campetella, Oscar

    2016-01-01

    Trypanosoma cruzi, the flagellate protozoan agent of Chagas disease or American trypanosomiasis, is unable to synthesize sialic acids de novo. Mucins and trans-sialidase (TS) are substrate and enzyme, respectively, of the glycobiological system that scavenges sialic acid from the host in a crucial interplay for T. cruzi life cycle. The acquisition of the sialyl residue allows the parasite to avoid lysis by serum factors and to interact with the host cell. A major drawback to studying the sialylation kinetics and turnover of the trypomastigote glycoconjugates is the difficulty to identify and follow the recently acquired sialyl residues. To tackle this issue, we followed an unnatural sugar approach as bioorthogonal chemical reporters, where the use of azidosialyl residues allowed identifying the acquired sugar. Advanced microscopy techniques, together with biochemical methods, were used to study the trypomastigote membrane from its glycobiological perspective. Main sialyl acceptors were identified as mucins by biochemical procedures and protein markers. Together with determining their shedding and turnover rates, we also report that several membrane proteins, including TS and its substrates, both glycosylphosphatidylinositol-anchored proteins, are separately distributed on parasite surface and contained in different and highly stable membrane microdomains. Notably, labeling for α(1,3)Galactosyl residues only partially colocalize with sialylated mucins, indicating that two species of glycosylated mucins do exist, which are segregated at the parasite surface. Moreover, sialylated mucins were included in lipid-raft-domains, whereas TS molecules are not. The location of the surface-anchored TS resulted too far off as to be capable to sialylate mucins, a role played by the shed TS instead. Phosphatidylinositol-phospholipase-C activity is actually not present in trypomastigotes. Therefore, shedding of TS occurs via microvesicles instead of as a fully soluble form. PMID

  11. Sialic Acid Glycobiology Unveils Trypanosoma cruzi Trypomastigote Membrane Physiology.

    PubMed

    Lantos, Andrés B; Carlevaro, Giannina; Araoz, Beatriz; Ruiz Diaz, Pablo; Camara, María de Los Milagros; Buscaglia, Carlos A; Bossi, Mariano; Yu, Hai; Chen, Xi; Bertozzi, Carolyn R; Mucci, Juan; Campetella, Oscar

    2016-04-01

    Trypanosoma cruzi, the flagellate protozoan agent of Chagas disease or American trypanosomiasis, is unable to synthesize sialic acids de novo. Mucins and trans-sialidase (TS) are substrate and enzyme, respectively, of the glycobiological system that scavenges sialic acid from the host in a crucial interplay for T. cruzi life cycle. The acquisition of the sialyl residue allows the parasite to avoid lysis by serum factors and to interact with the host cell. A major drawback to studying the sialylation kinetics and turnover of the trypomastigote glycoconjugates is the difficulty to identify and follow the recently acquired sialyl residues. To tackle this issue, we followed an unnatural sugar approach as bioorthogonal chemical reporters, where the use of azidosialyl residues allowed identifying the acquired sugar. Advanced microscopy techniques, together with biochemical methods, were used to study the trypomastigote membrane from its glycobiological perspective. Main sialyl acceptors were identified as mucins by biochemical procedures and protein markers. Together with determining their shedding and turnover rates, we also report that several membrane proteins, including TS and its substrates, both glycosylphosphatidylinositol-anchored proteins, are separately distributed on parasite surface and contained in different and highly stable membrane microdomains. Notably, labeling for α(1,3)Galactosyl residues only partially colocalize with sialylated mucins, indicating that two species of glycosylated mucins do exist, which are segregated at the parasite surface. Moreover, sialylated mucins were included in lipid-raft-domains, whereas TS molecules are not. The location of the surface-anchored TS resulted too far off as to be capable to sialylate mucins, a role played by the shed TS instead. Phosphatidylinositol-phospholipase-C activity is actually not present in trypomastigotes. Therefore, shedding of TS occurs via microvesicles instead of as a fully soluble form. PMID

  12. Preparation of PES ultrafiltration membranes with natural amino acids based zwitterionic antifouling surfaces

    NASA Astrophysics Data System (ADS)

    Xu, Chen; Liu, Xiaojiu; Xie, Binbin; Yao, Chen; Hu, Wenhan; Li, Yi; Li, Xinsong

    2016-11-01

    In this report, a simple and facile approach to enhance the antifouling property of poly(ether sulfone) (PES) ultrafiltration membrane was developed by grafting natural amino acids onto surface. First of all, poly(ether sulfone) composite membranes blended with poly(glycidyl methacrylate) were fabricated by phase inversion method followed by grafting of different types of natural amino acids onto the membrane surface through epoxy ring opening reaction. The analysis of attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) and X-ray photoelectron spectroscopy (XPS) verified the substantial enrichment of amino acids onto the surface of PES membranes. The hydrophilicity of the PES membranes was improved after grafting amino acids. The mechanical property and morphologies of the PES membranes proved that their basic performances were not obviously affected by grafting reaction, and these parameters were all still in the typical range for ultrafiltration membranes. The antifouling property of the grafted PES membranes against bovine serum albumin (BSA) and lysozyme (Lyz) was investigated in detail. It was found that PES membranes incorporated with neutral amino acids exhibited higher fouling resistance to both BSA and Lyz than the parent PES membrane. It can be ascribed to the formation of zwitterionic structure on the surface consisting of protonated secondary amino cations and carboxyl anions. Meanwhile, PES membranes grafted with charged amino acids had better antifouling properties against protein with same electric charges and improved adsorption related to protein with opposite electric charges. Furthermore, the ultrafiltration performance of the zwitterionic PES membranes was evaluated. The results showed that the modified membranes possessed of enhanced pure water flux, relative flux recovery and mildly lower rejection. The Darcy's Law analysis illustrated that the acidic amino acid grafted PES membranes had much lower permeation

  13. Phosphoric acid distribution and its impact on the performance of polybenzimidazole membranes

    NASA Astrophysics Data System (ADS)

    Mack, Florian; Heissler, Stefan; Laukenmann, Ruben; Zeis, Roswitha

    2014-12-01

    Phosphoric acid doped polybenzimidazole (PBI) is the most common membrane material for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC). The PBI membrane is usually doped by immersion in hot phosphoric acid. Immersion time and acid temperature affect the doping level of the membrane. In this work we studied the influence of doping time and temperature on the ex-situ and in-situ proton conductivities of poly (2, 5-benzimidazole) (AB-PBI) membranes as well as the fuel cell performance. Confocal Raman microscopy was employed to spatially resolve the acid distribution within the AB-PBI membranes. Therefore the interactions between the basic nitrogen-sides of the AB-PBI polymer and the phosphoric acid protons were investigated. We found that membranes with a 6 h doping time had significantly higher proton conductivity than those doped for only 3 h. In terms of absolute acid up-take, however, the difference was rather small. This result shows that the doping level alone does not define the conductivity of the membrane. The conductivity is also influenced by the micro acid distribution within the membrane. Highest membrane conductivity and fuel cell performance with fumapem AM cross-linked membranes were achieved with a doping time of 6 h and a doping temperature of 120 °C.

  14. Response of plasma membrane H+-ATPase in rice (Oryza sativa) seedlings to simulated acid rain.

    PubMed

    Liang, Chanjuan; Ge, Yuqing; Su, Lei; Bu, Jinjin

    2015-01-01

    Understanding the adaptation of plants to acid rain is important to find feasible approaches to alleviate such damage to plants. We studied effects of acid rain on plasma membrane H(+)-ATPase activity and transcription, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate during stress and recovery periods. Simulated acid rain at pH 5.5 did not affect plasma membrane H(+)-ATPase activity, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate. Plasma membrane H(+)-ATPase activity and transcription in leaves treated with acid rain at pH 3.5 was increased to maintain ion homeostasis by transporting excessive H(+) out of cells. Then intracellular H(+) was close to the control after a 5-day recovery, alleviating damage on membrane and sustaining photosynthetic efficiency and growth. Simulated acid rain at pH 2.5 inhibited plasma membrane H(+)-ATPase activity by decreasing the expression of H(+)-ATPase at transcription level, resulting in membrane damage and abnormal intracellular H(+), and reduction in photosynthetic efficiency and relative growth rate. After a 5-day recovery, all parameters in leaves treated with pH 2.5 acid rain show alleviated damage, implying that the increased plasma membrane H(+)-ATPase activity and its high expression were involved in repairing process in acid rain-stressed plants. Our study suggests that plasma membrane H(+)-ATPase can play a role in adaptation to acid rain for rice seedlings.

  15. Response of plasma membrane H+-ATPase in rice (Oryza sativa) seedlings to simulated acid rain.

    PubMed

    Liang, Chanjuan; Ge, Yuqing; Su, Lei; Bu, Jinjin

    2015-01-01

    Understanding the adaptation of plants to acid rain is important to find feasible approaches to alleviate such damage to plants. We studied effects of acid rain on plasma membrane H(+)-ATPase activity and transcription, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate during stress and recovery periods. Simulated acid rain at pH 5.5 did not affect plasma membrane H(+)-ATPase activity, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate. Plasma membrane H(+)-ATPase activity and transcription in leaves treated with acid rain at pH 3.5 was increased to maintain ion homeostasis by transporting excessive H(+) out of cells. Then intracellular H(+) was close to the control after a 5-day recovery, alleviating damage on membrane and sustaining photosynthetic efficiency and growth. Simulated acid rain at pH 2.5 inhibited plasma membrane H(+)-ATPase activity by decreasing the expression of H(+)-ATPase at transcription level, resulting in membrane damage and abnormal intracellular H(+), and reduction in photosynthetic efficiency and relative growth rate. After a 5-day recovery, all parameters in leaves treated with pH 2.5 acid rain show alleviated damage, implying that the increased plasma membrane H(+)-ATPase activity and its high expression were involved in repairing process in acid rain-stressed plants. Our study suggests that plasma membrane H(+)-ATPase can play a role in adaptation to acid rain for rice seedlings. PMID:25087500

  16. Effect of omega-3 fatty acids on the modification of erythrocyte membrane fatty acid content including oleic acid in peritoneal dialysis patients.

    PubMed

    An, W S; Lee, S M; Son, Y K; Kim, S E; Kim, K H; Han, J Y; Bae, H R; Park, Y

    2012-01-01

    Erythrocyte membrane fatty acids (FA), such as oleic acid, are related to acute coronary syndrome. There is no report about the effect of omega-3 FA on oleic acid in peritoneal dialysis (PD) patients. We hypothesized that omega-3 FA can modify erythrocyte membrane FA, including oleic acid, in PD patients. In a double-blind, randomized, placebo-controlled study, 18 patients who were treated with PD for at least 6 months were randomized to treatment for 12 weeks with omega-3 FA or placebo. Erythrocyte membrane FA content was measured by gas chromatography at baseline and after 12 weeks. The erythrocyte membrane content of eicosapentaenoic acid and docosahexaenoic acid was significantly increased and saturated FA and oleic acid were significantly decreased in the omega-3 FA supplementation group after 12 weeks compared to baseline. In conclusion, erythrocyte membrane FA content, including oleic acid, was significantly modified by omega-3 FA supplementation for 12 weeks in PD patients.

  17. Clofibric acid and gemfibrozil removal in membrane bioreactors.

    PubMed

    Gutierrez-Macias, Tania; Nacheva, Petia Mijaylova

    2015-01-01

    The removal of two blood lipid regulators, clofibric acid (CLA) and gemfibrozil (GFZ), was evaluated using two identical aerobic membrane bioreactors with 6.5 L effective volume each. Polysulfone ultrafiltration hollow fiber membranes were submerged in the reactors. Different operating conditions were tested varying the organic load (F/M), hydraulic residence time (HRT), biomass concentration measured as total suspended solids in the mixed liquor (MLTSS) and the sludge retention time (SRT). Complete GFZ removal was obtained with F/M of 0.21-0.48 kg COD kgTSS⁻¹ d⁻¹, HRT of 4-10 hours, SRT of 10-32 d and MLTSS of 6-10 g L⁻¹. The GFZ removal can be attributed to biodegradation and there was no accumulation of the compound in the biomass. The CLA removals improved with the SRT and HRT increase and F/M decrease. Average removals of 78-79% were obtained with SRT 16-32 d, F/M of 0.21-0.34 kgCOD kgTSS⁻¹ d⁻¹, HRT of 7-10 hours and MLTSS of 6-10 g L⁻¹. Biodegradation was found to be the main removal pathway.

  18. Erythrocyte Membrane Fatty Acid Composition in Premenopausal Patients with Iron Deficiency Anemia.

    PubMed

    Aktas, Mehmet; Elmastas, Mahfuz; Ozcicek, Fatih; Yilmaz, Necmettin

    2016-01-01

    Iron deficiency anemia (IDA) is one of the most common nutritional disorders in the world. In the present study, we evaluated erythrocyte membrane fatty acid composition in premenopausal patients with IDA. Blood samples of 102 premenopausal women and 88 healthy control subjects were collected. After the erythrocytes were separated from the blood samples, the membrane lipids were carefully extracted, and the various membrane fatty acids were measured by gas chromatography (GC). Statistical analyses were performed with the SPSS software program. We used blood ferritin concentration <15 ng/mL as cut-off for the diagnosis of IDA. The five most abundant individual fatty acids obtained were palmitic acid (16:0), oleic acid (18:1, n-9c), linoleic acid (18:2, n-6c), stearic acid (18:0), and erucic acid (C22:1, n-9c). These compounds constituted about 87% of the total membrane fatty acids in patients with IDA, and 79% of the total membrane fatty acids in the control group. Compared with control subjects, case patients had higher percentages of palmitic acid (29.9% case versus 25.3% control), oleic acid (16.8% case versus 15.1% control), and stearic acid (13.5% case versus 10.5% control), and lower percentages of erucic acid (11.5% case versus 13.6% control) and linoleic acid (15.2% case versus 15.4% control) in their erythrocyte membranes. In conclusion, the total-erythrocyte-membrane saturated fatty acid (SFA) composition in premenopausal women with IDA was found to be higher than that in the control group; however, the total-erythrocyte-membrane unsaturated fatty acid (UFA) composition in premenopausal women with IDA was found to be lower than that in the control group. The differences in these values were statistically significant.

  19. Separation of membranes from acid-solubilized fish muscle proteins with the aid of calcium ions and organic acids.

    PubMed

    Liang, Yong; Hultin, Herbert O

    2005-04-20

    Calcium chloride, and to a lesser extent MgCl2, aided in the separation of membranes by centrifugation from cod (Gadus morhua) muscle homogenates solubilized at pH 3 in the presence of citric acid or malic acid but not lactic acid. Adding citric acid and Ca2+ before solubilizing the cod muscle homogenates was needed for the effect. At 1 mM citric acid, 70-80% of the phospholipid and 25-30% of the protein were removed at 10 mM Ca2+. At 8 mM Ca2+, citric acid showed an optimal effect on phospholipid removal at 5 mM with 90% of the phospholipid and 35% of the protein removed. The treatment with citric acid and Ca2+ was also effective in separating the membrane from solubilized herring (Clupea harengus) muscle homogenate. Ca2+ and citric acid might exert their influence by disconnecting linkages between membranes and cytoskeletal proteins.

  20. Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells.

    PubMed

    Kent, C; Vagelos, P R

    1976-06-17

    Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.

  1. Effect of Sulfuric and Triflic Acids on the Hydration of Vanadium Cations: An ab Initio Study.

    PubMed

    Sepehr, Fatemeh; Paddison, Stephen J

    2015-06-01

    Vanadium redox flow batteries (VRFBs) may be a promising solution for large-scale energy storage applications, but the crossover of any of the redox active species V(2+), V(3+), VO(2+), and VO2(+) through the ion exchange membrane will result in self-discharge of the battery. Hence, a molecular level understanding of the states of vanadium cations in the highly acidic environment of a VRFB is needed. We examine the effects of sulfuric and triflic (CF3SO3H) acids on the hydration of vanadium species as they mimic the electrolyte and functional group of perfluorosulfonic acid (PFSA) membranes. Hybrid density functional theory in conjunction with a continuum solvation model was utilized to obtain the local structures of the hydrated vanadium cations in proximity to H2SO4, CF3SO3H, and their conjugate anions. The results indicate that none of these species covalently bond to the vanadium cations. The hydration structure of V(3+) is more distorted than that of V(2+) in an acidic medium. The oxo-group of VO2(+) is protonated by either acid, in contrast to VO(2+) which is not protonated. The atomic partial charge of the four oxidation states of vanadium varies from +1.7 to +2.0. These results provide the local solvation structures of vanadium cations in the VRFBs environment that are directly related to the electrolytes stability and diffusion of vanadium ions into the membrane. PMID:25954916

  2. Effect of Sulfuric and Triflic Acids on the Hydration of Vanadium Cations: An ab Initio Study.

    PubMed

    Sepehr, Fatemeh; Paddison, Stephen J

    2015-06-01

    Vanadium redox flow batteries (VRFBs) may be a promising solution for large-scale energy storage applications, but the crossover of any of the redox active species V(2+), V(3+), VO(2+), and VO2(+) through the ion exchange membrane will result in self-discharge of the battery. Hence, a molecular level understanding of the states of vanadium cations in the highly acidic environment of a VRFB is needed. We examine the effects of sulfuric and triflic (CF3SO3H) acids on the hydration of vanadium species as they mimic the electrolyte and functional group of perfluorosulfonic acid (PFSA) membranes. Hybrid density functional theory in conjunction with a continuum solvation model was utilized to obtain the local structures of the hydrated vanadium cations in proximity to H2SO4, CF3SO3H, and their conjugate anions. The results indicate that none of these species covalently bond to the vanadium cations. The hydration structure of V(3+) is more distorted than that of V(2+) in an acidic medium. The oxo-group of VO2(+) is protonated by either acid, in contrast to VO(2+) which is not protonated. The atomic partial charge of the four oxidation states of vanadium varies from +1.7 to +2.0. These results provide the local solvation structures of vanadium cations in the VRFBs environment that are directly related to the electrolytes stability and diffusion of vanadium ions into the membrane.

  3. Partitioning of amino acids into a model membrane: capturing the interface.

    PubMed

    Pogorelov, Taras V; Vermaas, Josh V; Arcario, Mark J; Tajkhorshid, Emad

    2014-02-13

    Energetics of protein side chain partitioning between aqueous solution and cellular membranes is of fundamental importance for correctly capturing the membrane binding and specific protein-lipid interactions of peripheral membrane proteins. We recently reported a highly mobile membrane mimetic (HMMM) model that accelerates lipid dynamics by modeling the membrane interior partially as a fluid organic solvent while retaining a literal description of the lipid head groups and the beginning of the tails. While the HMMM has been successfully applied to study spontaneous insertion of a number of peripheral proteins into membranes, a quantitative characterization of the energetics of membrane-protein interactions in HMMM membranes has not been performed. We report here the free energy profiles for partitioning of 10 protein side chain analogues into a HMMM membrane. In the interfacial and headgroup regions of the membrane, the side chain free energy profiles show excellent agreement with profiles previously reported for conventional membranes with full-tail lipids. In regions where the organic solvent is prevalent, the increased dipole and fluidity of the solvent generally result in a less accurate description, most notably overstabilization of aromatic and polar amino acids. As an additional measure of the ability of the HMMM model to describe membrane-protein interactions, the water-to-membrane interface transfer energies were analyzed and found to be in agreement with the previously reported experimental and computational hydrophobicity scales. We discuss strengths and weaknesses of HMMM in describing protein-membrane interactions as well as further development of model membranes. PMID:24451004

  4. Membrane engineering via trans unsaturated fatty acids production improves Escherichia coli robustness and production of biorenewables.

    PubMed

    Tan, Zaigao; Yoon, Jong Moon; Nielsen, David R; Shanks, Jacqueline V; Jarboe, Laura R

    2016-05-01

    Constructing microbial biocatalysts that produce biorenewables at economically viable yields and titers is often hampered by product toxicity. For production of short chain fatty acids, membrane damage is considered the primary mechanism of toxicity, particularly in regards to membrane integrity. Previous engineering efforts in Escherichia coli to increase membrane integrity, with the goal of increasing fatty acid tolerance and production, have had mixed results. Herein, a novel approach was used to reconstruct the E. coli membrane by enabling production of a novel membrane component. Specifically, trans unsaturated fatty acids (TUFA) were produced and incorporated into the membrane of E. coli MG1655 by expression of cis-trans isomerase (Cti) from Pseudomonas aeruginosa. While the engineered strain was found to have no increase in membrane integrity, a significant decrease in membrane fluidity was observed, meaning that membrane polarization and rigidity were increased by TUFA incorporation. As a result, tolerance to exogenously added octanoic acid and production of octanoic acid were both increased relative to the wild-type strain. This membrane engineering strategy to improve octanoic acid tolerance was found to require fine-tuning of TUFA abundance. Besides improving tolerance and production of carboxylic acids, TUFA production also enabled increased tolerance in E. coli to other bio-products, e.g. alcohols, organic acids, aromatic compounds, a variety of adverse industrial conditions, e.g. low pH, high temperature, and also elevated styrene production, another versatile bio-chemical product. TUFA permitted enhanced growth due to alleviation of bio-product toxicity, demonstrating the general effectiveness of this membrane engineering strategy towards improving strain robustness. PMID:26875445

  5. Interactions of amino acid side-chain analogs within membrane environments.

    PubMed

    Mirjalili, Vahid; Feig, Michael

    2015-02-19

    The interactions among four amino acid analog pairs (Asn, Ser, Phe, and Val) within the membrane environment were investigated using umbrella sampling molecular dynamics simulations. The results confirm generally expected qualitative trends of preferential association of polar compounds inside the membrane vs preferential interaction of hydrophobic compounds outside the membrane. Furthermore, correlations between amino acid interactions, membrane insertion, and membrane deformations are discussed and a detailed analysis of pair interaction energies is presented. A comparison of the energetics obtained from explicit lipid simulations with those from implicit membrane models reveals significant deviations and an improved parametrization of the heterogeneous dielectric generalized Born implicit model is provided that partially corrects for deficiencies in the implicit membrane model when compared with the new reference data from this study.

  6. Effects of nitrous acid exposure on human mucous membranes.

    PubMed

    Rasmussen, T R; Brauer, M; Kjaergaard, S

    1995-05-01

    Nitrous acid (HONO) is formed both indirectly from the reaction of nitrogen dioxide (NO2) with water on indoor surfaces, and directly during combustion. This gaseous pollutant may be a previously unrecognized causal factor in assessments of nitrogen oxide exposure effects. The present study is the first attempt to evaluate exposure effects of HONO on the human airways and the mucous membranes of the eyes and nose. Fifteen healthy adult nonsmokers were exposed for 3.5 h in a double-blind, balanced protocol to clean air, 77, and 395 ppb HONO. Each exposure was preceded by a 1-h baseline measurement period, and exposures were separated by 1 wk. There was a 10-min exercise period during exposure. Effects measurements included assessment of bronchial reactivity, measurement of specific airway conductance, spirometry, acoustic rhinometry, nasal lavage, tear-fluid cytology, a CO2 eye-provocation test, evaluation of eye redness, and subjective sensations. Effects of HONO exposure on the eyes were found as exposure-related changes in tear-fluid cytology. In particular, the number of squamous cells increased by 20, 67, and 80% following exposure to clean air, 77, and 395 ppb HONO, respectively (p = 0.004). Possible indications of exposure effects on sensitivity to CO2 eye provocation and on specific airway conductance were also measured. For specific airway conductance there was an approximate 10% decrease in conductance following exercise in association with HONO exposure, compared with a 2% decrease with clean air (p = 0.038).

  7. Nanostructured membranes and electrodes with sulfonic acid functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tripathi, Bijay P.; Schieda, M.; Shahi, Vinod K.; Nunes, Suzana P.

    Herein we report the covalent functionalization of multiwall carbon nanotubes by grafting sulfanilic acid and their dispersion into sulfonated poly(ether ether ketone). The nanocomposites were explored as an option for tuning the proton and electron conductivity, swelling, water and alcohol permeability aiming at nanostructured membranes and electrodes for application in alcohol or hydrogen fuel cells and other electrochemical devices. The nanocomposites were extensively characterized, by studying their physicochemical and electrochemical properties. They were processed as self-supporting films with high mechanical stability, proton conductivity of 4.47 × 10 -2 S cm -1 at 30 °C and 16.8 × 10 -2 S cm -1 at 80 °C and 100% humidity level, electron conductivity much higher than for the plain polymer. The methanol permeability could be reduced to 1/20, keeping water permeability at reasonable values. The ratio of bound water also increases with increasing content of sulfonated filler, helping in keeping water in the polymer in conditions of low external humidity level.

  8. Separate and Concentrate Lactic Acid Using Combination of Nanofiltration and Reverse Osmosis Membranes

    NASA Astrophysics Data System (ADS)

    Li, Yebo; Shahbazi, Abolghasem; Williams, Karen; Wan, Caixia

    The processes of lactic acid production include two key stages, which are (a) fermentation and (b) product recovery. In this study, free cell of Bifidobacterium longum was used to produce lactic acid from cheese whey. The produced lactic acid was then separated and purified from the fermentation broth using combination of nanofiltration and reverse osmosis membranes. Nanofiltration membrane with a molecular weight cutoff of 100-400 Da was used to separate lactic acid from lactose and cells in the cheese whey fermentation broth in the first step. The obtained permeate from the above nanofiltration is mainly composed of lactic acid and water, which was then concentrated with a reverse osmosis membrane in the second step. Among the tested nanofiltration membranes, HL membrane from GE Osmonics has the highest lactose retention (97±1%). In the reverse osmosis process, the ADF membrane could retain 100% of lactic acid to obtain permeate with water only. The effect of membrane and pressure on permeate flux and retention of lactose/lactic acid was also reported in this paper.

  9. The styrene-maleic acid copolymer: a versatile tool in membrane research.

    PubMed

    Dörr, Jonas M; Scheidelaar, Stefan; Koorengevel, Martijn C; Dominguez, Juan J; Schäfer, Marre; van Walree, Cornelis A; Killian, J Antoinette

    2016-01-01

    A new and promising tool in membrane research is the detergent-free solubilization of membrane proteins by styrene-maleic acid copolymers (SMAs). These amphipathic molecules are able to solubilize lipid bilayers in the form of nanodiscs that are bounded by the polymer. Thus, membrane proteins can be directly extracted from cells in a water-soluble form while conserving a patch of native membrane around them. In this review article, we briefly discuss current methods of membrane protein solubilization and stabilization. We then zoom in on SMAs, describe their physico-chemical properties, and discuss their membrane-solubilizing effect. This is followed by an overview of studies in which SMA has been used to isolate and investigate membrane proteins. Finally, potential future applications of the methodology are discussed for structural and functional studies on membrane proteins in a near-native environment and for characterizing protein-lipid and protein-protein interactions. PMID:26639665

  10. Distribution of sialic acid between sialoglycoproteins and other membrane components of different erythrocyte phenotypes.

    PubMed

    Udoh, A E

    1991-01-01

    The sialic acid content of erythrocytes of three different AB0 blood groups have been studied. The sialic acid contents of erythrocyte membranes containing 300 mg protein were determined and compared. Groups 0 (Rhesus negative), AB (both Rhesus negative and positive), and B (Rhesus negative) blood differed significantly (p less than 0.05) in total sialic acid content and in the distribution of sialic acid between sialoglycoproteins and other membrane components. Membrane materials containing 300 mg total protein showed sialic acid contents of 52.73 +/- 2.2 mumol sialic acid for group 0 (Rhesus negative) 34.77 +/- 1.16 mumol for group AB (Rh negative), 32.88 +/- 1.52 mumol for AB (Rh positive) and 21.23 +/- 0.84 mumol for B (Rh negative). In group 0 (Rh. neg.) membranes 39.4 +/- 1.4% of the total sialic acid was associated with the sialoglycoproteins. The percentage of sialic acids associated with sialoglycoproteins in other erythrocyte membranes were 77.7 +/- 1.3% for group B, and 55.6 +/- 1.0% and 56.4 +/- 1.8% for group AB (Rh. negative) and (Rh. positive) respectively. The changes appear to be independent of the Rhesus grouping but dependent on the AB0 grouping since membranes of the two Rhesus types of group AB had identical total sialic acid and sialoglycoproteins sialic acids. The sialic acid densities in sialoglycoproteins also differed from one erythrocyte type to another. Group 0 (Rh. negative) membrane sialoglycoproteins had sialic acid density of 140.5 +/- 3.1 nmol/mg compared to 71.7 +/- 1.2 nmol/mg for group B and 128.1 +/- 2.2 and 124.5 +/- 4.0 nmol/mg for group AB Rhesus negative and Rhesus positive respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Diffusion dialysis. Effect of membrane composition on acid/salt separation

    SciTech Connect

    Narebska, A.; Warszawski, A. )

    1992-05-01

    Diffusion dialysis is an energy-saving separation technique. In order to highlight the relationship between membrane composition and ability to separate acid/salt mixtures by diffusion dialysis, a few anion-exchange membranes were examined. Experiments on solubility/diffusivity phenomena were carried out in contact with hydrochloric acid and sodium chloride solutions (single- and two-solute experiments). Computations using Glueckauf and Tye models have indicated high nonuniformity in the distribution of fixed charged within the membranes and different accessibilities of the internal membrane volumes for the acid and salt. The Neosepta AFN-7 membrane (Tokuymam Soda Co.) has proved effective in differentiating the permeants by sorption (k{sub HCl}/k{sub NaCl} {approx} 2) and diffusivity ({bar D}{sub HCl}/{bar D}{sub NaCl} up to 10). This membrane is also the only one which, when in contact with two-solutes solutions, absorbs the acid preferentially to the salt. For this membrane the preferential sorption and transport of the acid depends not only on the physical structure of the membrane but also on the chemical nature of the polymer which contains pyridine moieties.

  12. Partitioning of Amino Acids into a Model Membrane: Capturing the Interface

    PubMed Central

    2015-01-01

    Energetics of protein side chain partitioning between aqueous solution and cellular membranes is of fundamental importance for correctly capturing the membrane binding and specific protein–lipid interactions of peripheral membrane proteins. We recently reported a highly mobile membrane mimetic (HMMM) model that accelerates lipid dynamics by modeling the membrane interior partially as a fluid organic solvent while retaining a literal description of the lipid head groups and the beginning of the tails. While the HMMM has been successfully applied to study spontaneous insertion of a number of peripheral proteins into membranes, a quantitative characterization of the energetics of membrane–protein interactions in HMMM membranes has not been performed. We report here the free energy profiles for partitioning of 10 protein side chain analogues into a HMMM membrane. In the interfacial and headgroup regions of the membrane, the side chain free energy profiles show excellent agreement with profiles previously reported for conventional membranes with full-tail lipids. In regions where the organic solvent is prevalent, the increased dipole and fluidity of the solvent generally result in a less accurate description, most notably overstabilization of aromatic and polar amino acids. As an additional measure of the ability of the HMMM model to describe membrane–protein interactions, the water-to-membrane interface transfer energies were analyzed and found to be in agreement with the previously reported experimental and computational hydrophobicity scales. We discuss strengths and weaknesses of HMMM in describing protein–membrane interactions as well as further development of model membranes. PMID:24451004

  13. Performance of a cross-flow humidifier with a high flux water vapor transport membrane

    NASA Astrophysics Data System (ADS)

    Ahluwalia, R. K.; Wang, X.; Johnson, W. B.; Berg, F.; Kadylak, D.

    2015-09-01

    Water vapor transport (WVT) flux across a composite membrane that consists of a very thin perfluorosulfonic acid (PFSA) ionomer layer sandwiched between two expanded polytetrafluoroethylene (PTFE) microporous layers is investigated. Static and dynamic tests are conducted to measure WVT flux for different composite structures; a transport model shows that the underlying individual resistances for water diffusion in the gas phase and microporous and ionomer layers and for interfacial kinetics of water uptake at the ionomer surface are equally important under different conditions. A finite-difference model is formulated to determine water transport in a full-scale (2-m2 active membrane area) planar cross-flow humidifier module assembled using pleats of the optimized composite membrane. In agreement with the experimental data, the modeled WVT flux in the module increases at higher inlet relative humidity (RH) of the wet stream and at lower pressures, but the mass transfer effectiveness is higher at higher pressures. The model indicates that the WVT flux is highest under conditions that maintain the wet stream at close to 100% RH while preventing the dry stream from becoming saturated. The overall water transport is determined by the gradient in RH of the wet and dry streams but is also affected by vapor diffusion in the gas layer and the microporous layer.

  14. Performance of a Cross-Flow Humidifier with a High Flux Water Vapor Transport Membrane

    SciTech Connect

    Ahluwalia, R. K.; Wang, X.; Johnson, W. B.; Berg, F.; Kadylak, D.

    2015-09-30

    Water vapor transport (WVT) flux across a composite membrane that consists of a very thin perfluorosulfonic acid (PFSA) ionomer layer sandwiched between two expanded polytetrafluoroethylene (PTFE) microporous layers is investigated. Static and dynamic tests are conducted to measure WVT flux for different composite structures; a transport model shows that the underlying individual resistances for water diffusion in the gas phase and microporous and ionomer layers and for interfacial kinetics of water uptake at the ionomer surface are equally important under different conditions. A finite-difference model is formulated to determine water transport in a full-scale (2-m2 active membrane area) planar cross-flow humidifier module assembled using pleats of the optimized composite membrane. In agreement with the experimental data, the modeled WVT flux in the module increases at higher inlet relative humidity (RH) of the wet stream and at lower pressures, but the mass transfer effectiveness is higher at higher pressures. The model indicates that the WVT flux is highest under conditions that maintain the wet stream at close to 100% RH while preventing the dry stream from becoming saturated. The overall water transport is determined by the gradient in RH of the wet and dry streams but is also affected by vapor diffusion in the gas layer and the microporous layer.

  15. Fatty acid composition of erythrocyte membrane lipid obtained from children suffering from kwashiorkor and marasmus.

    PubMed

    Vajreswari, A; Narayanareddy, K; Rao, P S

    1990-08-01

    The fatty acid composition of erythrocyte membrane (EM) lipids obtained from normal, kwashiorkor, and marasmic children was analyzed by gas chromatography. The proportion of palmitic acid (16:0) was lower and of oleic acid (18:1) higher in the kwashiorkor group than in the control group. The marasmic group showed lower proportions of eicosatrienoic acid (20:3) and arachidonic acid (20:4) and a higher proportion of oleic acid (18:1) than the control group. A significant difference was found between the marasmic and kwashiorkor groups with respect to arachidonic acid (20:4), which showed a lower proportion in the former group than the latter. The ratio of arachidonic acid to linoleic acid (20:4/18:2) was markedly lower in the marasmic group than the control group, suggesting a possible impairment in the conversion of linoleic acid to arachidonic acid in marasmic children. The ratio of unsaturated fatty acids to saturated fatty acids was markedly elevated in the kwashiorkor group over that of control group, indicating increased fluidity of EM in kwashiorkor. It is suggested that the altered membrane fatty acid composition reflects deranged lipid metabolism and affects the physical and physiological properties of EM and could contribute to changes in the activities of several red blood cell membrane-bound enzymes reported earlier in kwashiorkor children.

  16. Bile acids modulate signaling by functional perturbation of plasma membrane domains.

    PubMed

    Zhou, Yong; Maxwell, Kelsey N; Sezgin, Erdinc; Lu, Maryia; Liang, Hong; Hancock, John F; Dial, Elizabeth J; Lichtenberger, Lenard M; Levental, Ilya

    2013-12-13

    Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.

  17. Effect of surface and membrane potentials on IAA (indoleactic acid) uptake and binding by zucchini membrane vesicles

    SciTech Connect

    Clark, K.A.; Goldsmith, M.H.M.

    1986-08-01

    The polar transport of the endogenous hormone controlling extension growth of plant cells, indoleacetic acid (IAA), is thought to depend on transmembrane pH and electrical gradients resulting in part from the action of proton ATPases in the plasma membrane. Elements of this transport process are permeation of the membrane by the undissociated lipophilic indoleacetic acid (IAAH) from the acidic apoplast, followed by dissociation of the weak acid and accumulation of the IAA anion (IAA/sup -/) in the alkaline cytoplasm; a saturable symport of IAA/sup -/ with one or more protons; a carrier-mediated efflux of IAA/sup -/ down a considerable electrochemical gradient. The efflux is greater from the basal than the apical end of cells and is thought to be responsible for the overall polarity of the process. This step is also the site of action of napthylphthalamic acid (NPA) and herbicides that inhibit polar transport but stimulate net accumulation of auxin by tissues and cells. We are using membrane vesicles as a simplified system for studying the mechanisms involved in the transport and accumulation of auxin. In particular, we are interested in determining the involvement of the transmembrane pH (pH/sub o/ < pH/sub i/) and voltage gradients (K/sup +/ diffusion potential, (K/sup +/)/sub in/ > (K/sup +/)/sub out/) in IAA uptake. 19 refs., 6 figs.

  18. Microviscosity of cucumber (Cucumis sativus L.) fruit protoplast membranes is altered by triacontanol and abscisic acid.

    PubMed

    Shripathi, V; Swamy, G S; Chandrasekhar, K S

    1997-01-31

    Cucumber (Cucumis sativus L.) fruit protoplast membranes were probed with diphenylhexatriene (DPH) and pyrene, and also with two different plant growth regulators, triacontanol (TRIA) and abscisic acid (ABA). Fluorescence anisotropies of DPH and pyrene were measured after incorporating them into the membranes. The fluorescence lifetime of membrane-bound pyrene was also measured by using neodymium-doped yttrium aluminium garnet (Nd:YAG) laser of 35 ps pulses. The microviscosities of the membranes were calculated using the values of fluorescence anisotropy and lifetime. In the presence of TRIA and ABA, there was a sharp decrease in the fluorescence lifetime of pyrene. Similarly, there was also a decrease in the microviscosities of the membranes and increase in the rate of rotation of membrane-bound fluorophore, induced by the plant growth regulators. Furthermore, TRIA or TRIA + ABA could reduce the fluorescence anisotropy of both the fluorophores whereas, ABA decreased the anisotropy of only pyrene. This property of ABA may be due to its confinement to a specific spacial facet in the membrane. Fatty acid analysis indicated that membrane microviscosity fluctuations were not due to altered fatty acid composition alone as it is known that change in lipid-protein interaction would also alter the physical status of the membrane.

  19. Nanoscale Distribution of Sulfonic Acid Groups Determines Structure and Binding of Water in Nafion Membranes

    PubMed Central

    Ling, Xiao; Bonn, Mischa

    2016-01-01

    Abstract The connection between the nanoscale structure of two chemically equivalent, yet morphologically distinct Nafion fuel‐cell membranes and their macroscopic chemical properties is demonstrated. Quantification of the chemical interactions between water and Nafion reveals that extruded membranes have smaller water channels with a reduced sulfonic acid head group density compared to dispersion‐cast membranes. As a result, a disproportionally large amount of non‐bulk water molecules exists in extruded membranes, which also exhibit larger proton conductivity and larger water mobility compared to cast membranes. The differences in the physicochemical properties of the membranes, that is, the chemical constitution of the water channels and the local water structure, and the accompanying differences in macroscopic water and proton transport suggest that the chemistry of nanoscale channels is an important, yet largely overlooked parameter that influences the functionality of fuel‐cell membranes. PMID:26895211

  20. Nanoscale Distribution of Sulfonic Acid Groups Determines Structure and Binding of Water in Nafion Membranes.

    PubMed

    Ling, Xiao; Bonn, Mischa; Parekh, Sapun H; Domke, Katrin F

    2016-03-14

    The connection between the nanoscale structure of two chemically equivalent, yet morphologically distinct Nafion fuel-cell membranes and their macroscopic chemical properties is demonstrated. Quantification of the chemical interactions between water and Nafion reveals that extruded membranes have smaller water channels with a reduced sulfonic acid head group density compared to dispersion-cast membranes. As a result, a disproportionally large amount of non-bulk water molecules exists in extruded membranes, which also exhibit larger proton conductivity and larger water mobility compared to cast membranes. The differences in the physicochemical properties of the membranes, that is, the chemical constitution of the water channels and the local water structure, and the accompanying differences in macroscopic water and proton transport suggest that the chemistry of nanoscale channels is an important, yet largely overlooked parameter that influences the functionality of fuel-cell membranes.

  1. Refsum disease diagnostic marker phytanic acid alters the physical state of membrane proteins of liver mitochondria.

    PubMed

    Schönfeld, P; Struy, H

    1999-08-27

    Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid), a branched chain fatty acid accumulating in Refsum disease to high levels throughout the body, induces uncoupling of rat liver mitochondria similar to non-branched fatty acids (e.g. palmitic acid), but the contribution of the ADP/ATP carrier or the aspartate/glutamate carrier in phytanic acid-induced uncoupling is of minor importance. Possible deleterious effects of phytanic acid on membrane-linked energy coupling processes were studied by ESR spectroscopy using rat liver mitochondria and a membrane preparation labeled with the lipid-specific spin probe 5-doxylstearic acid (5-DSA) or the protein-specific spin probe MAL-TEMPO (4-maleimido-2,2,6, 6-tetramethyl-piperidine-1-oxyl). The effects of phytanic acid on phospholipid molecular dynamics and on the physical state of membrane proteins were quantified by estimation of the order parameter or the ratio of the amplitudes of the weakly to strongly immobilized MAL-TEMPO binding sites (W/S ratio), respectively. It was found, that phytanic acid (1) increased the mobility of phospholipid molecules (indicated by a decrease in the order parameter) and (2) altered the conformational state and/or the segmental mobility of membrane proteins (indicated by a drastic decrease in the W/S ratio). Unsaturated fatty acids with multiple cis-double bonds (e.g. linolenic or arachidonic acid), but not non-branched FFA (ranging from chain length C10:0 to C18:0), also decrease the W/S ratio. It is hypothesized that the interaction of phytanic acid with transmembrane proteins might stimulate the proton permeability through the mitochondrial inner membrane according to a mechanism, different to a protein-supported fatty acid cycling.

  2. [Study of antioxidant and membrane activity of rosmarinic acid using different model systems].

    PubMed

    Popov, A M; Osipov, A N; Korepanova, E A; Krivoshapko, O N; Artiukov, A A

    2013-01-01

    Rosmarinic acid is found in many species of different families of higher plants and its chemical structure is phenol propanoid with various biological activity. In this paper, we conducted a comparative study of antioxidant (radical-scavenging) properties of rosmarinic acid in systems of 2,2'-azo-bis(2-methylpropionamidin)dihydrochloride-luminol and hemoglobin-hydrogen peroxide-lu- minol, determined its protective potential in preventing peroxidation of linoleic acid, and evaluated the effect on the permeability of planar bilayer lipid membranes. Linoleic acid peroxidation was assessed by iron-thiocyanate method. In these studies, trolox was used as a reference antioxidant, and ascorbic acid, and dihydroquercetin were taken as standards. Rosmarinic acid is significantly superior to trolox, ascorbic acid and dihydroquercetin in the tests for antioxidant activity in the systems studied, as well as in inhibition of linoleic acid peroxidation. According to their activity the investigated substances can be arranged in the following order: rosmarinic acid > dihydroquercetin trolox > ascorbic acid. Rosmarinic acid does not cause significant changes in the permeability of planar bilayer membranes in a dose range of 0.5 to 10 mkg/mL. Antioxidant activity of rosmarinic acid is due to the neutralization of reactive oxygen species and/or luminol radicals generated in model systems. The observed features of the antioxidant and membrane activity of rosmarinic acid, which may underlie the previously mentioned pharmacological effects are discussed. PMID:25481945

  3. Modification of ultrafiltration membrane with nanoscale zerovalent iron layers for humic acid fouling reduction.

    PubMed

    Ma, Baiwen; Yu, Wenzheng; Jefferson, William A; Liu, Huijuan; Qu, Jiuhui

    2015-03-15

    Nanoscale zerovalent iron (NZVI) was layered onto ultrafiltration (UF) membrane surface and tested for antifouling properties using humic acid (HA). Scanning electron microscopy showed that a relatively homogeneous layer was formed across the membrane surface by NZVI particles. Strong adhesion was observed between NZVI and UF membrane used. HA was significantly removed and membrane flux was increased in the presence of NZVI layer. Increased loadings of NZVI onto the membrane surface increased resistance to fouling while slightly reducing the clean water permeability of the membrane. However, the pore size of the layer formed by pristine NZVI was large, resulting in more chances of HA molecules getting to the membrane surface even blocking the membrane pores at the beginning. Membrane loaded with NZVI layer performed much better under acidic conditions. During NZVI synthesis, specific surface area of NZVI particle increased with increasing the ratio of ethanol (Vethanol/Vsolution), which also gradually decreased the average pore size of NZVI layer. As a result, the corresponding membrane flux steadily increased. Additionally, the results for permeate samples under different conditions showed that large molecular weight (MW, >30 kDa) and medium MW HA molecules (3-30 kDa) were removed much faster than those of small MW HA molecules (<3 kDa). PMID:25613411

  4. Membrane-directed effects of the plant hormones abscisic acid, indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid.

    PubMed

    Schauf, C L; Bringle, B; Stillwell, W

    1987-03-30

    This study examines two ways plant hormones might influence membrane processes, effects on overall permeability and modifications of specific ion channels. Abscisic acid (ABA) and indole-3-acetic acid (IAA) greatly enhanced erythritol permeability in mixed egg lecithin bilayers. In single component dioleoylphosphatidylcholine bilayers ABA was less effective than IAA, while 2,4-dichlorophenoxyacetate (2,4-D) did not affect either system or alter their ABA response. In Myxicola axons ABA and IAA had no effect, while 2,4-D (10 uM) caused a depolarizing shift of voltage-dependent Na+ and K+ activation by 25 +/- 4 mV and 15 +/- 3 mV, consistent with internal negative surface charge changes of -0.002 e-/A2 and -0.0007 e-/A2. We conclude that both generalized and ion channel-directed effects may link plant hormones and intracellular regulation.

  5. Metabolism and longevity: is there a role for membrane fatty acids?

    PubMed

    Hulbert, A J

    2010-11-01

    More than 100 years ago, Max Rubner combined the fact that both metabolic rate and longevity of mammals varies with body size to calculate that "life energy potential" (lifetime energy turnover per kilogram) was relatively constant. This calculation linked longevity to aerobic metabolism which in turn led to the "rate-of-living" and ultimately the "oxidative stress" theories of aging. However, the link between metabolic rate and longevity is imperfect. Although unknown in Rubner's time, one aspect of body composition of mammals also varies with body size, namely the fatty acid composition of membranes. Fatty acids vary dramatically in their susceptibility to peroxidation and the products of lipid peroxidation are very powerful reactive molecules that damage other cellular molecules. The "membrane pacemaker" modification of the "oxidative stress" theory of aging proposes that fatty acid composition of membranes, via its influence on peroxidation of lipids, is an important determinant of lifespan (and a link between metabolism and longevity). The relationship between membrane fatty acid composition and longevity is discussed for (1) mammals of different body size, (2) birds of different body size, (3) mammals and birds that are exceptionally long-living for their size, (4) strains of mice that vary in longevity, (5) calorie-restriction extension of longevity in rodents, (6) differences in longevity between queen and worker honeybees, and (7) variation in longevity among humans. Most of these comparisons support an important role for membrane fatty acid composition in the determination of longevity. It is apparent that membrane composition is regulated for each species. Provided the diet is not deficient in polyunsaturated fat, it has minimal influence on a species' membrane fatty acid composition and likely also on it's maximum longevity. The exceptional longevity of Homo sapiens combined with the limited knowledge of the fatty acid composition of human tissues

  6. Adsorptive Membranes vs. Resins for Acetic Acid Removal from Biomass Hydrolysates

    SciTech Connect

    Han, B.; Carvalho, W.; Canilha, L.; da Silva, S. S.; e Silva, J. B. A.; McMillan, J. D.; Wickramasinghe, S. R.

    2006-01-01

    Acetic acid is a compound commonly found in hemicellulosic hydrolysates. This weak acid strongly influences the bioconversion of sugar containing hydrolysates. Previous investigators have used anion exchange resins for acetic acid removal from different hemicellulosic hydrolysates. In this study, the efficiency of an anion exchange membrane was compared to that of an anion exchange resin, for acetic acid removal from a DI water solution and an acidic hemicellulose hydrolysate pretreated using two different methods. Ion exchange membranes and resins have very different geometries. Here the performance of membranes and resins is compared using two dimensionless parameters, the relative mass throughput and chromatographic bed number. The relative mass throughput arises naturally from the Thomas solution for ion exchange. The results show that the membrane exhibit better performance in terms of capacity, and loss of the desired sugars. In addition acetic acid may be eluted at a higher concentration from the membrane thus leading to the possibility of recovery and re-use of the acetic acid.

  7. Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion

    SciTech Connect

    Idupulapati, Nagesh B.; Devanathan, Ramaswami; Dupuis, Michel

    2011-03-31

    We used classical molecular dynamics (MD) simulations to investigate the nanoscale morphology and proton transport properties of perfluoro phosphonic (FPA) and phosphinic acid (FPA-I) membranes as they are being considered for use in low temperature fuel cells. We systematically investigated these properties as a function of the hydration level. The changes in nanostructure, in transport dynamics of water and hydronium ions, and in water network percolation were extracted from MD simulations and compared with Nafion. Phosphonic and phosphinic acid moieties in FPA and FPA-I, have lower acidity than sulfonic acid in Nafion, yet the diffusion of water was observed to be faster in FPA and FPA-I than in Nafion, particularly at low hydration levels. However this did not give rise to notable differences in hydronium ion diffusion and water network percolation for these membranes over Nafion. Similar observations were also reported by our group recently in a study of perfluoro-sulfonyl imide membranes carrying stronger super-acids than sulfonic acid of Nafion. These findings together suggest no strong apparent correlation between the acidity strength of the functional acid groups and the dynamics of water and hydronium ions in hydrated polymer electrolyte membranes (PEMs) with similar fluorocarbon backbones and acidic group-carrying side chains. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  8. A Comparative Study of Phosphoric Acid-doped m-PBI Membranes

    SciTech Connect

    Perry, Kelly A; More, Karren Leslie; Payzant, E Andrew; Meisner, Roberta A; Sumpter, Bobby G; Benicewicz, Brian

    2014-01-01

    Phosphoric acid (PA)-doped m-polybenzimidazole (PBI) membranes used in high temperature fuel cells and hydrogen pumps were prepared by a conventional imbibing process and a sol-gel fabrication process. A comparative study was conducted to investigate the critical properties of PA doping levels, ionic conductivities, mechanical properties, and molecular ordering. This systematic study found that sol-gel PA-doped m-PBI membranes were able to absorb higher acid doping levels and to achieve higher ionic conductivities than conventionally imbibed membranes when treated in an equivalent manner. Even at similar acid loadings, the sol-gel membranes exhibited higher ionic conductivities. Heat treatment of conventionally imbibed membranes with 29wt% solids caused a significant reduction in mechanical properties; conversely, sol-gel membranes exhibited an enhancement in mechanical properties. From X-ray structural studies and atomistic simulations, both conventionally imbibed and sol-gel membranes exhibited d-spacings of 3.5 and 4.6 , which were tentatively attributed to parallel ring stacking and staggered side-to-side packing, respectively, of the imidazole rings in these aromatic hetercyclic polymers. An anisotropic staggered side-to-side chain packing present in the conventional membranes may be root to the reduction in mechanical properties.

  9. Roles played by acidic lipids in HIV-1 Gag membrane binding.

    PubMed

    Olety, Balaji; Ono, Akira

    2014-11-26

    The MA domain mediates plasma membrane (PM) targeting of HIV-1 Gag, leading to particle assembly at the PM. The interaction between MA and acidic phospholipids, in addition to N-terminal myristoyl moiety, promotes Gag binding to lipid membranes. Among acidic phospholipids, PI(4,5)P2, a PM-specific phosphoinositide, is essential for proper HIV-1 Gag localization to the PM and efficient virus particle production. Recent studies further revealed that MA-bound RNA negatively regulates HIV-1 Gag membrane binding and that PI(4,5)P2 is necessary to overcome this RNA-imposed block. In this review, we will summarize the current understanding of Gag-membrane interactions and discuss potential roles played by acidic phospholipids.

  10. Synthesis of nucleic acid probes on membrane supports: a procedure for the removal of unincorporated precursors.

    PubMed

    Bhat, S P

    1990-01-01

    We have used DNA bound to small pieces of nylon membrane for the synthesis of radioactive probes. The DNA to be used for generating the probe(s) is first bound to nylon membranes and then introduced into the reaction mix. The labeling reaction takes place on the membrane and therefore allows easy removal of unincorporated precursors by simple washing for 1-2 min. The clean labeled probe is eluted from the membrane in formamide or in water and is ready for use. This DNA-membrane can be stored for reuse. Synthesis of probes on a solid support such as nylon membrane thus circumvents problems associated with chromatographic manipulations needed for the separation of labeled DNA from unicorporated precursors. Probes synthesized in this manner are as efficient in detecting nucleic acid sequences as those synthesized in solution. PMID:2321760

  11. NOVEL POLY-GLUTAMIC ACID FUNCTIONALIZED MICROFILTRATION MEMBRANES FOR SORPTION OF HEAVY METALS AT HIGH CAPACITY

    EPA Science Inventory

    Various sorbent/ion exchange materials have been reported in the literature for metal ion entrapment. We have developed a highly innovative and new approach to obtain high metal pick-up utilizing poly-amino acids (poly-L-glutamic acid, 14,000 MW) covalently attached to membrane p...

  12. Gallic acid-grafted-chitosan inhibits foodborne pathogens by a membrane damage mechanism.

    PubMed

    Lee, Dae-Sung; Je, Jae-Young

    2013-07-01

    In this study, antimicrobial activity of gallic acid-grafted-chitosans (gallic acid-g-chitosans) against five Gram-positive and five Gram-negative foodborne pathogens was evaluated. The minimum inhibitory concentrations (MICs) of gallic acid-g-chitosans ranged from 16 to 64 μg/mL against Gram-positive bacteria and ranged from 128 to 512 μg/mL against Gram-negative bacteria. These activities were higher than those of unmodified chitosan. The bactericidal activity of gallic acid-g-chitosan (I), which showed the highest antimicrobial activity, was evaluated by time-killing assay with multiples of MIC, and it was recognized to depend on its dose. The integrity of cell membrane, outer membrane (OM), inner membrane (IM) permeabilization experiments, and transmission electron microscopy (TEM) observation were conducted for elucidation of the detailed antimicrobial mode of action of gallic acid-g-chitosan. Results showed that treatment of gallic acid-g-chitosan (I) quickly increased the release of intracellular components for both Escherichia coli and Staphylococcus aureus. In addition, gallic acid-g-chitosan (I) also rapidly increased the 1-N-phenylanphthylamine (NPN) uptake and the release of β-galactosidase via increasing the permeability of OM and IM in E. coli. TEM observation demonstrated that gallic acid-g-chitosan (I) killed the bacteria via disrupting the cell membrane.

  13. The bile acid-sensitive ion channel (BASIC) is activated by alterations of its membrane environment.

    PubMed

    Schmidt, Axel; Lenzig, Pia; Oslender-Bujotzek, Adrienne; Kusch, Jana; Lucas, Susana Dias; Gründer, Stefan; Wiemuth, Dominik

    2014-01-01

    The bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC family of ion channels. Channels of this family are characterized by a common structure, their physiological functions and modes of activation, however, are diverse. Rat BASIC is expressed in brain, liver and intestinal tract and activated by bile acids. The physiological function of BASIC and its mechanism of bile acid activation remain a puzzle. Here we addressed the question whether amphiphilic bile acids activate BASIC by directly binding to the channel or indirectly by altering the properties of the surrounding membrane. We show that membrane-active substances other than bile acids also affect the activity of BASIC and that activation by bile acids and other membrane-active substances is non-additive, suggesting that BASIC is sensitive for changes in its membrane environment. Furthermore based on results from chimeras between BASIC and ASIC1a, we show that the extracellular and the transmembrane domains are important for membrane sensitivity.

  14. Acid-base and chelatometric photo-titrations with photosensors and membrane photosensors.

    PubMed

    Matsuo, T; Masuda, Y; Sekido, E

    1986-08-01

    Photosensors (PS) and membrane photosensors (MPS), which can be immersed in the test solution and facilitate the measurement of concentration, have been developed by miniaturizing an optical system consisting of a light source and a photocell. For use in acid-base or complexometric titrations a poly(vinyl chloride) membrane containing an acid-base or metallochromic indicator can be applied as a coating to the photocell. Spectrophotometric determination of copper(II), and photometric acid-base and chelatometric titrations have been performed with the PS and MPS systems.

  15. A boron phosphate-phosphoric acid composite membrane for medium temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Mamlouk, M.; Scott, K.

    2015-07-01

    A composite membrane based on a non-stoichiometric composition of BPO4 with excess of PO4 (BPOx) was synthesised and characterised for medium temperature fuel cell use (120-180 °C). The electrolyte was characterised by FTIR, SS-NMR, TGA and XRD and showed that the B-O is tetrahedral, in agreement with reports in the literature that boron phosphorus oxide compounds at B:P < 1 are exclusively built of borate and phosphate tetrahedra. Platinum micro electrodes were used to study the electrolyte compatibility and stability towards oxygen reduction at 150 °C and to obtain kinetic and mass transport parameters. The conductivities of the pure BPOx membrane electrolyte and a Polybenzimidazole (PBI)-4BPOx composite membrane were 7.9 × 10-2 S cm-1 and 4.5 × 10-2 S cm-1 respectively at 150 °C, 5%RH. Fuel cell tests showed a significant enhancement in performance of BPOx over that of typical 5.6H3PO4-PBI membrane electrolyte. The enhancement is due to the improved ionic conductivity (3×), a higher exchange current density of the oxygen reduction (30×) and a lower membrane gas permeability (10×). Fuel cell current densities at 0.6 V were 706 and 425 mA cm-2 for BPOx and 5.6H3PO4-PBI, respectively, at 150 °C with O2 (atm).

  16. Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles.

    PubMed

    Chen, Irene A; Szostak, Jack W

    2004-05-25

    Electrochemical proton gradients are the basis of energy transduction in modern cells, and may have played important roles in even the earliest cell-like structures. We have investigated the conditions under which pH gradients are maintained across the membranes of fatty acid vesicles, a model of early cell membranes. We show that pH gradients across such membranes decay rapidly in the presence of alkali-metal cations, but can be maintained in the absence of permeable cations. Under such conditions, when fatty acid vesicles grow through the incorporation of additional fatty acid, a transmembrane pH gradient is spontaneously generated. The formation of this pH gradient captures some of the energy released during membrane growth, but also opposes and limits further membrane area increase. The coupling of membrane growth to energy storage could have provided a growth advantage to early cells, once the membrane composition had evolved to allow the maintenance of stable pH gradients.

  17. Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

    DOEpatents

    Horwitz, Earl Philip; Gatrone, Ralph Carl; Nash, Kenneth LaVerne

    1997-01-01

    Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

  18. Rh polypeptide is a major fatty acid-acylated erythrocyte membrane protein

    SciTech Connect

    de Vetten, M.P.; Agre, P.

    1988-12-05

    The erythrocyte Rh antigens contain an Mr = 32,000 integral protein which is thought to contribute in some way to the organization of surrounding phospholipid. To search for possible fatty acid acylation of the Rh polypeptide, intact human erythrocytes were incubated with (3H)palmitic acid prior to preparation of membranes and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Several membrane proteins were labeled, but none corresponded to the glycophorins or membrane proteins 1-8. An Mr = 32,000 band was prominently labeled on Rh (D)-negative and -positive erythrocytes and could be precipitated from the latter with anti-D. No similar protein was labeled on membranes from Rhmod erythrocytes, a rare phenotype lacking Rh antigens. Labeling of the Rh polypeptide most likely represents palmitic acid acylation through thioester linkages. The 3H label was not extracted with chloroform/methanol, but was quantitatively eluted with hydroxylamine and co-chromatographed with palmitohydroxamate and free palmitate by thin layer chromatography. The fatty acid acylations occurred independent of protein synthesis and were completely reversed by chase with unlabeled palmitate. It is concluded that the Rh polypeptide is fatty acid-acylated, being a major substrate of an acylation-deacylation mechanism associated with the erythrocyte membrane.

  19. A self-humidifying acidic-alkaline bipolar membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Peng, Sikan; Xu, Xin; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

    2015-12-01

    To maintain membrane hydration and operate effectively, polymer electrolyte membrane fuel cells (PEMFCs) require elaborate water management, which significantly increases the complexity and cost of the fuel cell system. Here we propose a novel and entirely different approach to membrane hydration by exploiting the concept of bipolar membranes. Bipolar membrane (BPM) fuel cells utilize a composite membrane consisting of an acidic polymer electrolyte membrane on the anode side and an alkaline electrolyte membrane on the cathode side. We present a novel membrane electrode assembly (MEA) fabrication method and demonstrate experimentally and theoretically that BPM fuel cells can (a) self-humidify to ensure high ionic conductivity; and (b) allow use of non-platinum catalysts due to inherently faster oxygen reduction kinetics on an alkaline cathode. Our Pt-based BPM fuel cell achieves a two orders of magnitude gain in power density of 327 mW cm-2 at 323 K under dry gas feed, the highest power output achieved under anhydrous operation conditions. A theoretical analysis and in situ measurements are presented to characterize the unique interfacial water generation and transport behavior that make self-humidification possible during operation. Further optimization of these features and advances in fabricating bipolar MEAs would open the way for a new generation of self-humidifying and water-management-free PEMFCs.

  20. Separation of macromolecular proteins and removal of humic acid by cellulose acetate modified UF membranes.

    PubMed

    Kanagaraj, P; Nagendran, A; Rana, D; Matsuura, T

    2016-08-01

    Surface modifying macromolecules (SMMs) were synthesized with various polyurethane pre polymers end-capped with different groups and blended into the casting solution of cellulose acetate (CA) to prepare surface modified ultra-filtration (UF) membranes for water filtration applications. The surface modification of the CA membranes was confirmed by the FTIR and static contact angle (SCA) measurements. The membranes so prepared had the typical characteristics of UF membranes as confirmed by scanning electron microscopy (SEM). Membrane properties were studied in terms of membrane compaction, percentage water content (%WC), pure water flux (PWF), membrane hydraulic resistance (Rm), molecular weight cut-off (MWCO), average pore size and porosity. The result showed that PWF, %WC, MWCO and pore size increased whereas the Rm decreased by the addition of SMMs. The significant effect of SMMs on the fouling by humic acid (HA) was also observed. It was found that the cSMM-3 membrane, in which SMM was synthesized with diethylene glycol (DEG) and hydroxyl benzene sulfonate (HBS) was blended, had the highest flux recovery ratio FRR (84.6%), as well as the lowest irreversible fouling (15.4%), confirming their improved antifouling properties. Thus, the SMM modified CA membranes had proven, to play an important role in the water treatment by UF. PMID:27118046

  1. Separation of macromolecular proteins and removal of humic acid by cellulose acetate modified UF membranes.

    PubMed

    Kanagaraj, P; Nagendran, A; Rana, D; Matsuura, T

    2016-08-01

    Surface modifying macromolecules (SMMs) were synthesized with various polyurethane pre polymers end-capped with different groups and blended into the casting solution of cellulose acetate (CA) to prepare surface modified ultra-filtration (UF) membranes for water filtration applications. The surface modification of the CA membranes was confirmed by the FTIR and static contact angle (SCA) measurements. The membranes so prepared had the typical characteristics of UF membranes as confirmed by scanning electron microscopy (SEM). Membrane properties were studied in terms of membrane compaction, percentage water content (%WC), pure water flux (PWF), membrane hydraulic resistance (Rm), molecular weight cut-off (MWCO), average pore size and porosity. The result showed that PWF, %WC, MWCO and pore size increased whereas the Rm decreased by the addition of SMMs. The significant effect of SMMs on the fouling by humic acid (HA) was also observed. It was found that the cSMM-3 membrane, in which SMM was synthesized with diethylene glycol (DEG) and hydroxyl benzene sulfonate (HBS) was blended, had the highest flux recovery ratio FRR (84.6%), as well as the lowest irreversible fouling (15.4%), confirming their improved antifouling properties. Thus, the SMM modified CA membranes had proven, to play an important role in the water treatment by UF.

  2. Plant pentacyclic triterpenic acids as modulators of lipid membrane physical properties.

    PubMed

    Prades, Jesús; Vögler, Oliver; Alemany, Regina; Gomez-Florit, Manuel; Funari, Sérgio S; Ruiz-Gutiérrez, Valentina; Barceló, Francisca

    2011-03-01

    Free triterpenic acids (TTPs) present in plants are bioactive compounds exhibiting multiple nutriceutical activities. The underlying molecular mechanisms have only been examined in part and mainly focused on anti-inflammatory properties, cancer and cardiovascular diseases, in all of which TTPs frequently affect membrane-related proteins. Based on the structural characteristics of TTPs, we assume that their effect on biophysical properties of cell membranes could play a role for their biological activity. In this context, our study is focused on the compounds, oleanolic (3β-hydroxy-12-oleanen-28-oic acid, OLA), maslinic (2α,3β-dihydroxy-12-oleanen-28-oic acid, MSL) and ursolic ((3β)-3-hydroxyurs-12-en-28-oic acid, URL) as the most important TTPs present in orujo olive oil. X-ray diffraction, differential scanning calorimetry, (31)P nuclear magnetic resonance and Laurdan fluorescence data provide experimental evidence that OLA, MSL and URL altered the structural properties of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and DPPC-Cholesterol (Cho) rich membranes, being located into the polar-hydrophobic interphase. Specifically, in DPPC membranes, TTPs altered the structural order of the L(β'), phase without destabilizing the lipid bilayer. The existence of a nonbilayer isotropic phase in coexistence with the liquid crystalline L(α) phase, as observed in DPPC:URL samples, indicated the presence of lipid structures with high curvature (probably inverted micelles). In DPPC:Cho membranes, TTPs affected the membrane phase properties increasing the Laurdan GP values above 40°C. MSL and URL induced segregation of Cho within the bilayer, in contrast to OLA, that reduced the structural organization of the membrane. These results strengthen the relevance of TTP interactions with cell membranes as a molecular mechanism underlying their broad spectrum of biological effects.

  3. Fatty acid remodeling by LPCAT3 enriches arachidonate in phospholipid membranes and regulates triglyceride transport

    PubMed Central

    Hashidate-Yoshida, Tomomi; Harayama, Takeshi; Hishikawa, Daisuke; Morimoto, Ryo; Hamano, Fumie; Tokuoka, Suzumi M; Eto, Miki; Tamura-Nakano, Miwa; Yanobu-Takanashi, Rieko; Mukumoto, Yoshiko; Kiyonari, Hiroshi; Okamura, Tadashi; Kita, Yoshihiro; Shindou, Hideo; Shimizu, Takao

    2015-01-01

    Polyunsaturated fatty acids (PUFAs) in phospholipids affect the physical properties of membranes, but it is unclear which biological processes are influenced by their regulation. For example, the functions of membrane arachidonate that are independent of a precursor role for eicosanoid synthesis remain largely unknown. Here, we show that the lack of lysophosphatidylcholine acyltransferase 3 (LPCAT3) leads to drastic reductions in membrane arachidonate levels, and that LPCAT3-deficient mice are neonatally lethal due to an extensive triacylglycerol (TG) accumulation and dysfunction in enterocytes. We found that high levels of PUFAs in membranes enable TGs to locally cluster in high density, and that this clustering promotes efficient TG transfer. We propose a model of local arachidonate enrichment by LPCAT3 to generate a distinct pool of TG in membranes, which is required for normal directionality of TG transfer and lipoprotein assembly in the liver and enterocytes. DOI: http://dx.doi.org/10.7554/eLife.06328.001 PMID:25898003

  4. Semicontinuous Production of Lactic Acid From Cheese Whey Using Integrated Membrane Reactor

    NASA Astrophysics Data System (ADS)

    Li, Yebo; Shahbazi, Abolghasem; Coulibaly, Sekou; Mims, Michele M.

    Semicontinuous production of lactic acid from cheese whey using free cells of Bifidobacterium longum with and without nanofiltration was studied. For the semicontinuous fermentation without membrane separation, the lactic acid productivity of the second and third runs is much lower than the first run. The semicontinuous fermentation with nanoseparation was run semicontinuously for 72 h with lactic acid to be harvested every 24 h using a nanofiltration membrane unit. The cells and unutilized lactose were kept in the reactor and mixed with newly added cheese whey in the subsequent runs. Slight increase in the lactic acid productivity was observed in the second and third runs during the semicontinuous fermentation with nanofiltration. It can be concluded that nanoseparation could improve the lactic acid productivity of the semicontinuous fermentation process.

  5. Nature and nurture in atherosclerosis: The roles of acylcarnitine and cell membrane-fatty acid intermediates.

    PubMed

    Blair, Harry C; Sepulveda, Jorge; Papachristou, Dionysios J

    2016-03-01

    Macrophages recycle components of dead cells, including cell membranes. When quantities of lipids from cell membranes of dead cells exceed processing capacity, phospholipid and cholesterol debris accumulate as atheromas. Plasma lipid profiles, particularly HDL and LDL cholesterol, are important tools to monitor atherosclerosis risk. Membrane lipids are exported, as triglycerides or phospholipids, or as cholesterol or cholesterol esters, via lipoproteins for disposal, for re-use in cell membranes, or for fat storage. Alternative assays evaluate other aspects of lipid pathology. A key process underlying atherosclerosis is backup of macrophage fatty acid catabolism. This can be quantified by accumulation of acylcarnitine intermediates in extracellular fluid, a direct assay of adequacy of β-oxidation to deal with membrane fatty acid recycling. Further, membranes of somatic cells, such as red blood cells (RBC), incorporate fatty acids that reflect dietary intake. Changes in RBC lipid composition occur within days of ingesting modified fats. Since diets with high saturated fat content or artificial trans-fatty acids promote atherosclerosis, RBC lipid content shifts occur with atherosclerosis, and can show cellular adaptation to pathologically stiff membranes by increased long-chain doubly unsaturated fatty acid production. Additional metabolic changes with atherosclerosis of potential utility include inflammatory cytokine production, modified macrophage signaling pathways, and altered lipid-handling enzymes. Even after atherosclerotic lesions appear, approaches to minimize macrophage overload by reducing rate of fat metabolism are promising. These include preventive measures, and drugs including statins and the newer PCSK9 inhibitors. New cell-based biochemical and cytokine assays provide data to prevent or monitor atherosclerosis progression. PMID:26133667

  6. Nature and nurture in atherosclerosis: The roles of acylcarnitine and cell membrane-fatty acid intermediates.

    PubMed

    Blair, Harry C; Sepulveda, Jorge; Papachristou, Dionysios J

    2016-03-01

    Macrophages recycle components of dead cells, including cell membranes. When quantities of lipids from cell membranes of dead cells exceed processing capacity, phospholipid and cholesterol debris accumulate as atheromas. Plasma lipid profiles, particularly HDL and LDL cholesterol, are important tools to monitor atherosclerosis risk. Membrane lipids are exported, as triglycerides or phospholipids, or as cholesterol or cholesterol esters, via lipoproteins for disposal, for re-use in cell membranes, or for fat storage. Alternative assays evaluate other aspects of lipid pathology. A key process underlying atherosclerosis is backup of macrophage fatty acid catabolism. This can be quantified by accumulation of acylcarnitine intermediates in extracellular fluid, a direct assay of adequacy of β-oxidation to deal with membrane fatty acid recycling. Further, membranes of somatic cells, such as red blood cells (RBC), incorporate fatty acids that reflect dietary intake. Changes in RBC lipid composition occur within days of ingesting modified fats. Since diets with high saturated fat content or artificial trans-fatty acids promote atherosclerosis, RBC lipid content shifts occur with atherosclerosis, and can show cellular adaptation to pathologically stiff membranes by increased long-chain doubly unsaturated fatty acid production. Additional metabolic changes with atherosclerosis of potential utility include inflammatory cytokine production, modified macrophage signaling pathways, and altered lipid-handling enzymes. Even after atherosclerotic lesions appear, approaches to minimize macrophage overload by reducing rate of fat metabolism are promising. These include preventive measures, and drugs including statins and the newer PCSK9 inhibitors. New cell-based biochemical and cytokine assays provide data to prevent or monitor atherosclerosis progression.

  7. [Reverse osmosis membrane fouling by humic acid using XDLVO approach: effect of calcium ions].

    PubMed

    Yao, Shu-Di; Gao, Xin-Yu; Guo, Ben-Hua; Bao, Nan; Xie, Hui-Jun; Liang, Shuang

    2012-06-01

    Interfacial interactions involved in reverse osmosis (RO) membrane fouling by humic acid were quantitatively evaluated using the XDLVO (extended Derjaguin-Landau-Verwey-Overbeek) approach. The role of each individual interfacial interaction during membrane fouling was elucidated with special emphasis devoted into the influence of Ca2+ under different solution pHs. The results showed that, regardless of the presence of Ca2+, van der Waals interaction favoring fouling contributed the most to the interfacial interactions at pH 3, whereas the polar interaction inhibiting fouling played a dominant role at pH 7 and pH 10. Electrostatic double layer interaction appeared to be the weakest in all cases, thus contributing the least to membrane fouling. It was the changing of polar interaction that gave rise to the influence of Ca2+ on membrane fouling, which turned out to be more significant at lower pH. Ca2+ would accelerate humic acid RO membrane fouling at most cases. Correlation analysis between interfacial free energy and fouling extent revealed that XDLVO approach could reasonably predict humic acid RO membrane fouling behaviors under different solution conditions.

  8. Fluorinated Aromatic Amino Acids Distinguish Cation-π Interactions from Membrane Insertion.

    PubMed

    He, Tao; Gershenson, Anne; Eyles, Stephen J; Lee, Yan-Jiun; Liu, Wenshe R; Wang, Jiangyun; Gao, Jianmin; Roberts, Mary F

    2015-07-31

    Cation-π interactions, where protein aromatic residues supply π systems while a positive-charged portion of phospholipid head groups are the cations, have been suggested as important binding modes for peripheral membrane proteins. However, aromatic amino acids can also insert into membranes and hydrophobically interact with lipid tails. Heretofore there has been no facile way to differentiate these two types of interactions. We show that specific incorporation of fluorinated amino acids into proteins can experimentally distinguish cation-π interactions from membrane insertion of the aromatic side chains. Fluorinated aromatic amino acids destabilize the cation-π interactions by altering electrostatics of the aromatic ring, whereas their increased hydrophobicity enhances membrane insertion. Incorporation of pentafluorophenylalanine or difluorotyrosine into a Staphylococcus aureus phosphatidylinositol-specific phospholipase C variant engineered to contain a specific PC-binding site demonstrates the effectiveness of this methodology. Applying this methodology to the plethora of tyrosine residues in Bacillus thuringiensis phosphatidylinositol-specific phospholipase C definitively identifies those involved in cation-π interactions with phosphatidylcholine. This powerful method can easily be used to determine the roles of aromatic residues in other peripheral membrane proteins and in integral membrane proteins. PMID:26092728

  9. Fluorinated Aromatic Amino Acids Distinguish Cation-π Interactions from Membrane Insertion*

    PubMed Central

    He, Tao; Gershenson, Anne; Eyles, Stephen J.; Lee, Yan-Jiun; Liu, Wenshe R.; Wang, Jiangyun; Gao, Jianmin; Roberts, Mary F.

    2015-01-01

    Cation-π interactions, where protein aromatic residues supply π systems while a positive-charged portion of phospholipid head groups are the cations, have been suggested as important binding modes for peripheral membrane proteins. However, aromatic amino acids can also insert into membranes and hydrophobically interact with lipid tails. Heretofore there has been no facile way to differentiate these two types of interactions. We show that specific incorporation of fluorinated amino acids into proteins can experimentally distinguish cation-π interactions from membrane insertion of the aromatic side chains. Fluorinated aromatic amino acids destabilize the cation-π interactions by altering electrostatics of the aromatic ring, whereas their increased hydrophobicity enhances membrane insertion. Incorporation of pentafluorophenylalanine or difluorotyrosine into a Staphylococcus aureus phosphatidylinositol-specific phospholipase C variant engineered to contain a specific PC-binding site demonstrates the effectiveness of this methodology. Applying this methodology to the plethora of tyrosine residues in Bacillus thuringiensis phosphatidylinositol-specific phospholipase C definitively identifies those involved in cation-π interactions with phosphatidylcholine. This powerful method can easily be used to determine the roles of aromatic residues in other peripheral membrane proteins and in integral membrane proteins. PMID:26092728

  10. Pervaporation of Water from Aqueous Sulfuric Acid at Elevated Temperatures Using Nafion® Membranes

    SciTech Connect

    Christopher J. Orme; Frederick F. Stewart

    2009-01-01

    The concentration of sulfuric acid by pervaporation has been studied using Nafion-112® and Nafion-117® membranes, which have been characterized in terms of flux, permeability, and selectivity at 100 ºC and 120 ºC. Feed concentrations investigated ranged from 40 to over 80 weight percent. In general, water fluxes ranged from 100-8000 g/m2h, depending on feed acid concentration and separations factors as high as 104 were observed. Membrane stability was probed using Dynamic Mechanical Analysis that revealed some embrittlement of the membranes during use. Further studies showed that the embrittlement was due to an interaction with the acid and was not induced by the operating temperature.

  11. Positronium Formation Of Glyeisdyl Methacrylic Acid (GMA)/Styrene Grafted On PVDF Membrane For Fuel Cells

    SciTech Connect

    Abdel-Hady, E. E.; Abdel-Hamed, M. O.; Eltonny, M. M.

    2011-06-01

    Simultaneous gamma irradiation was used effectively for grafting of glycidyl methacrylic acid and styrene onto Poly vinyldine fluoride (PVDF). Membranes were characterized by thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The properties of the obtained membranes were evaluated in terms of proton conductivity, methanol permeability and positron annihilation lifetime (PALS) parameters. The high probability of Positronium formation enables the application of PALS to the study of free volume. Good property values approved the applicability of the membrane from the cost benefit point of view.

  12. Pervaporation separation of ethanol-water mixtures using polyacrylic acid composite membranes

    DOEpatents

    Neidlinger, H.H.

    1985-05-07

    Synthetic, organic, polymeric membranes were prepared from polyacrylic acid salts for use with pervaporation apparatus in the separation of ehthanol-water mixtures. The polymeric material was prepared in dilute aqueous solution and coated onto a polysulfone support film, from which excess polymeric material was subsequently removed. Cross-links were then generated by limited exposure to toluene-2,4-diisocyanata solution, after which the prepared membrane was heat-cured. The resulting membrane structure showed selectivity in permeating water over a wide range of feed concentrations. 4 tabs.

  13. Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes.

    PubMed

    Abidin, Muhammad Nidzhom Zainol; Goh, Pei Sean; Ismail, Ahmad Fauzi; Othman, Mohd Hafiz Dzarfan; Hasbullah, Hasrinah; Said, Noresah; Kadir, Siti Hamimah Sheikh Abdul; Kamal, Fatmawati; Abdullah, Mohd Sohaimi; Ng, Be Cheer

    2016-11-01

    Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm(-2)h(-1) to 95.36Lm(-2)h(-1) upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application. PMID:27524052

  14. Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2[S

    PubMed Central

    Oninla, Vincent O.; Breiden, Bernadette; Babalola, Jonathan O.; Sandhoff, Konrad

    2014-01-01

    During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747–1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion. PMID:25339683

  15. Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2.

    PubMed

    Oninla, Vincent O; Breiden, Bernadette; Babalola, Jonathan O; Sandhoff, Konrad

    2014-12-01

    During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747-1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion.

  16. Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2.

    PubMed

    Oninla, Vincent O; Breiden, Bernadette; Babalola, Jonathan O; Sandhoff, Konrad

    2014-12-01

    During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747-1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion. PMID:25339683

  17. Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis.

    PubMed

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2013-09-01

    The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) - namely carbamazepine and sulfamethoxazole - in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores.

  18. Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis.

    PubMed

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2013-09-01

    The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) - namely carbamazepine and sulfamethoxazole - in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores. PMID:23764606

  19. Interplay between structure and relaxations in perfluorosulfonic acid proton conducting membranes.

    PubMed

    Giffin, Guinevere A; Haugen, Gregory M; Hamrock, Steven J; Di Noto, Vito

    2013-01-16

    This study focuses on changes in the structure of ionomer membranes, provided by the 3M Fuel Cells Component Group, as a function of the equivalent weight (EW) and the relationship between the structure and the properties of the membrane. Wide-angle X-ray diffraction results showed evidence of both non-crystalline and crystalline ordered hydrophobic regions in all the EW membranes except the 700 EW membrane. The spectral changes evident in the vibrational spectra of the 3M membranes can be associated with two major phenomena: (1) dissociation of the proton from the sulfonic acid groups even in the presence of small amounts of water; and (2) changes in the conformation or the degree of crystallinity of the poly(tetrafluoroethylene) hydrophobic domains both as a function of EW and membrane water content. All the membranes, regardless of EW, are thermally stable up to 360 °C. The wet membranes have conductivities between 7 and 20 mS/cm at 125 °C. In this condition, the conductivity values follow VTF behavior, which suggests that the proton migration occurs via proton exchange processes between delocalization bodies (DBs) that are facilitated by the dynamics of the host polymer. The conductivity along the interface between the hydrophobic and hydrophilic domains makes a larger contribution in the smaller EW membranes likely due to the existence of a greater number of interfaces in the membrane. The larger crystalline domains present in the higher EW membranes provide percolation pathways for charge migration between DBs, which reduces the probability of charge transfer along the interface. Therefore, at higher EWs although there is charge migration along the interface within the hydrophobic-hydrophilic domains, the exchange of protons between different DBs is likely the rate-limiting step of the overall conduction process. PMID:23249300

  20. Direct sensing of total acidity by chronopotentiometric flash titrations at polymer membrane ion-selective electrodes.

    PubMed

    Gemene, Kebede L; Bakker, Eric

    2008-05-15

    Polymer membrane ion-selective electrodes containing lipophilic ionophores are traditionally interrogated by zero current potentiometry, which, ideally, gives information on the sample activity of ionic species. It is shown here that a discrete cathodic current pulse across an H (+)-selective polymeric membrane doped with the ionophore ETH 5294 may be used for the chronopotentiometric detection of pH in well-buffered samples. However, a reduction in the buffer capacity leads to large deviations from the expected Nernstian response slope. This is explained by the local depletion of hydrogen ions at the sample-membrane interface as a result of the galvanostatically imposed ion flux in direction of the membrane. This depletion is found to be a function of the total acidity of the sample and can be directly monitored chronopotentiometrically in a flash titration experiment. The subsequent application of a baseline potential pulse reverses the extraction process of the current pulse, allowing one to interrogate the sample with minimal perturbation. In one protocol, total acidity is found to be proportional to the magnitude of applied current at the flash titration end point. More conveniently, the square root of the flash titration end point time observed at a fixed applied current is a linear function of the total acid concentration. This suggests that it is possible to perform rapid localized pH titrations at ion-selective electrodes without the need for volumetric titrimetry. The technique is explored here for acetic acid, MES and citric acid with promising results. Polymeric membrane electrodes based on poly(vinyl chloride) plasticized with o-nitrophenyl octyl ether in a 1:2 mass ratio may be used for the detection of acids of up to ca. 1 mM concentration, with flash titration times on the order of a few seconds. Possible limitations of the technique are discussed, including variations of the acid diffusion coefficients and influence of electrical migration.

  1. Acylation of keratinocyte transglutaminase by palmitic and myristic acids in the membrane anchorage region

    SciTech Connect

    Chakravarty, R.; Rice, R.H.

    1989-01-05

    The membrane-bound form of keratinocyte transglutaminase was found to be labeled by addition of (/sup 3/H) acetic, (/sup 3/H)myristic, or (/sup 3/H)palmitic acids to the culture medium of human epidermal cells. Acid methanolysis and high performance liquid chromatography analysis of palmitate-labeled transglutaminase yielded only methyl palmitate. In contrast, analysis of the myristate-labeled protein yielded approximately 40% methyl myristate and 60% methyl palmitate. Incorporation of neither label was significantly affected by cycloheximide inhibition of protein synthesis. The importance of the fatty acid moiety for membrane anchorage was demonstrated in three ways. First, the enzyme was solubilized from the particulate fraction of cell extracts by treatment with neutral 1 M hydroxylamine, which was sufficient to release the fatty acid label. Second, solubilization of active enzyme from the particulate fraction upon mild trypsin treatment resulted in a reduction in size by approximately 10 kDa and removal of the fatty acid radiolabels. Third, the small fraction of soluble transglutaminase in cell extracts was found almost completely to lack fatty acid labeling. Keratinocyte transglutaminase translated from poly(A+) RNA in a reticulocyte cell-free system was indistinguishable in size from the native enzyme, suggesting anchorage requires only minor post-translational processing. Thus, the data are highly compatible with membrane anchorage by means of fatty acid acylation within 10 kDa of the NH/sub 2/ or COOH terminus.

  2. Phospholipid fatty acid turnover in erythrocyte membranes from humans exposed to hyperbaric hyperoxia

    SciTech Connect

    Davis, M.A.

    1988-01-01

    The purpose of this investigation was to examine phospholipid fatty acid turnover in erythrocyte membranes from human subjects exposed to hyperbaric, hyperoxic conditions. Seven males breathed 100% oxygen at two atmospheres of pressure for nine hours. Venous blood was collected one hour before the oxygen exposure; one hour, five hours, and nine hours into the exposure; and one hour, 24 hours, 48 hours and one week after the exposure ended. Washed erythrocytes were incubated with ({sup 3}H) oleic acid for thirty minutes at 37{degree}C. Phospholipids were extracted with methanol and chloroform, separated by thin layer chromatography, and quantitated by spectrodensitometry. Radioactivity was measured in four phospholipid classes and incorporation of ({sup 3}H) oleic acid into phospholipids calculated. Phospholipid fatty acid turnover was used as an indicator of membrane metabolism.

  3. Effect of various concentration of sulfuric acid for Nafion membrane activation on the performance of fuel cell

    NASA Astrophysics Data System (ADS)

    Pujiastuti, Sri; Onggo, Holia

    2016-02-01

    This work proposes an activation treatment to Nafion 117 membrane with sulfuric acid in various concentrations. The main goal of this study is to increase the Nafion 117 membrane performance, which is determined by proton number in the membrane and membrane performance in Polymer Electrolyte Membrane Fuel Cell (PEMFC). This work was developed using sulfuric acids in four different concentrations: 1, 2, 3, and 4 M. The surface morphology and functional groups of activated membranes were studied using Scanning Electron Microscope and Fourier Transform Infrared, respectively. The proton number absorbed in membranes was observed by gravimetric measurements. The performances of activated membranes in PEMFC were studied by single cell measurements with H2/O2 operation. The experimental results showed that activation of Nafion membrane did not change its surface morphology and functional groups. The proton number increased when the concentration of sulfuric acid is increased from 1 to 3 M and from 1 to 4 M. On the other hand, there is no significant increase when the concentration of sulfuric acid was increased from 1 to 2 M. Similar trends were observed when testing activated membrane performance in PEMFC, especially for current density at 0.6 V and maximum power. It is assumed that there is a correlation between the increase of sulfuric acid concentration in activation process with the increase of proton number in the membrane that are available for facilitating of transfer protons from the anode to the cathode.

  4. Fatty acid membrane assembly on coacervate microdroplets as a step towards a hybrid protocell model.

    PubMed

    Dora Tang, T-Y; Rohaida Che Hak, C; Thompson, Alexander J; Kuimova, Marina K; Williams, D S; Perriman, Adam W; Mann, Stephen

    2014-06-01

    Mechanisms of prebiotic compartmentalization are central to providing insights into how protocellular systems emerged on the early Earth. Protocell models are based predominantly on the membrane self-assembly of fatty-acid vesicles, although membrane-free scenarios that involve liquid-liquid microphase separation (coacervation) have also been considered. Here we integrate these alternative models of prebiotic compartmentalization and develop a hybrid protocell model based on the spontaneous self-assembly of a continuous fatty-acid membrane at the surface of preformed coacervate microdroplets prepared from cationic peptides/polyelectrolytes and adenosine triphosphate or oligo/polyribonucleotides. We show that the coacervate-supported membrane is multilamellar, and mediates the selective uptake or exclusion of small and large molecules. The coacervate interior can be disassembled without loss of membrane integrity, and fusion and growth of the hybrid protocells can be induced under conditions of high ionic strength. Our results highlight how notions of membrane-mediated compartmentalization, chemical enrichment and internalized structuration can be integrated in protocell models via simple chemical and physical processes.

  5. Fatty acid membrane assembly on coacervate microdroplets as a step towards a hybrid protocell model

    NASA Astrophysics Data System (ADS)

    Dora Tang, T.-Y.; Rohaida Che Hak, C.; Thompson, Alexander J.; Kuimova, Marina K.; Williams, D. S.; Perriman, Adam W.; Mann, Stephen

    2014-06-01

    Mechanisms of prebiotic compartmentalization are central to providing insights into how protocellular systems emerged on the early Earth. Protocell models are based predominantly on the membrane self-assembly of fatty-acid vesicles, although membrane-free scenarios that involve liquid-liquid microphase separation (coacervation) have also been considered. Here we integrate these alternative models of prebiotic compartmentalization and develop a hybrid protocell model based on the spontaneous self-assembly of a continuous fatty-acid membrane at the surface of preformed coacervate microdroplets prepared from cationic peptides/polyelectrolytes and adenosine triphosphate or oligo/polyribonucleotides. We show that the coacervate-supported membrane is multilamellar, and mediates the selective uptake or exclusion of small and large molecules. The coacervate interior can be disassembled without loss of membrane integrity, and fusion and growth of the hybrid protocells can be induced under conditions of high ionic strength. Our results highlight how notions of membrane-mediated compartmentalization, chemical enrichment and internalized structuration can be integrated in protocell models via simple chemical and physical processes.

  6. Fatty acid membrane assembly on coacervate microdroplets as a step towards a hybrid protocell model.

    PubMed

    Dora Tang, T-Y; Rohaida Che Hak, C; Thompson, Alexander J; Kuimova, Marina K; Williams, D S; Perriman, Adam W; Mann, Stephen

    2014-06-01

    Mechanisms of prebiotic compartmentalization are central to providing insights into how protocellular systems emerged on the early Earth. Protocell models are based predominantly on the membrane self-assembly of fatty-acid vesicles, although membrane-free scenarios that involve liquid-liquid microphase separation (coacervation) have also been considered. Here we integrate these alternative models of prebiotic compartmentalization and develop a hybrid protocell model based on the spontaneous self-assembly of a continuous fatty-acid membrane at the surface of preformed coacervate microdroplets prepared from cationic peptides/polyelectrolytes and adenosine triphosphate or oligo/polyribonucleotides. We show that the coacervate-supported membrane is multilamellar, and mediates the selective uptake or exclusion of small and large molecules. The coacervate interior can be disassembled without loss of membrane integrity, and fusion and growth of the hybrid protocells can be induced under conditions of high ionic strength. Our results highlight how notions of membrane-mediated compartmentalization, chemical enrichment and internalized structuration can be integrated in protocell models via simple chemical and physical processes. PMID:24848239

  7. Double liquid membrane system for the removal of actinides and lanthanides from acidic nuclear wastes

    SciTech Connect

    Chiarizia, R.; Danesi, P.R.

    1985-01-01

    Supported liquid membranes (SLM), consisting of an organic solution of n-octyl-(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl-phosphate (TBP) in decalin are able to perform selective separation and concentration of actinide and lanthanide ions from aqueous nitrate feed solutions and synthetic nuclear wastes. In the membrane process a possible strip solution is a mixture of formic acid and hydroxylammonium formate (HAF). The effectiveness of this strip solution is reduced and eventually nullified by the simultaneous transfer through the SLM of nitric acid which accumulates in the strip solution. A possible way to overcome this drawback is to make use of a second SLM consisting of a primary amine which is able to extract only HNO/sub 3/ from the strip solution. In this work the results obtained by experimentally studying the membrane system: synthetic nuclear waste/CMPO-TBP membrane/HCOOH-HAF strip solution/primary amine membrane/NaOH solution, are reported. They show that the use of a second liquid membrane is effective in controlling the HNO/sub 3/ concentration in the strip solution, thus allowing the actinide and lanthanide ions removal from the feed solution to proceed to completion. 15 refs., 10 figs., 1 tab.

  8. Dicarboxylic acids with limited numbers of hydrocarbons stabilize cell membrane and increase osmotic resistance in rat erythrocytes.

    PubMed

    Mineo, Hitoshi; Amita, Nozomi; Kawawake, Megumi; Higuchi, Ayaka

    2013-11-01

    We examined the effect of dicarboxylic acids having 0 to 6 hydrocarbons and their corresponding monocarboxylic or tricarboxylic acids in changing the osmotic fragility (OF) in rat red blood cells (RBCs). Malonic, succinic, glutaric and adipic acids, which are dicarboxylic acids with 1, 2, 3 and 4 straight hydrocarbons located between two carboxylic groups, decreased the OF in a concentration-dependent manner. Other long-chain dicarboxylic acids did not change the OF in rat RBCs. The benzoic acid derivatives, isophthalic and terephthalic acids, but not phthalic acid, decreased the OF in a concentration-dependent manner. Benzene-1,2,3-tricarboxylic acid, but not benzene-1,3,5-tricarboxylic acid, also decreased the OF in rat RBCs. On the other hand, monocarboxylic acids possessing 2 to 7 straight hydrocarbons and benzoic acid increased the OF in rat RBCs. In short-chain dicarboxylic acids, a limited number of hydrocarbons between the two carboxylic groups are thought to form a V- or U-shaped structure and interact with phospholipids in the RBC membrane. In benzene dicarboxylic and tricarboxylic acids, a part of benzene nucleus between the two carboxylic groups is thought to enter the plasma membrane and act on acyl-chain in phospholipids in the RBC membrane. For dicarboxylic and tricarboxylic acids, limited numbers of hydrocarbons in molecules are speculated to enter the RBC membrane with the hydrophilic carboxylic groups remaining outside, stabilizing the structure of the cell membrane and resulting in an increase in osmotic resistance in rat RBCs.

  9. Spectrum of Membrane Morphological Responses to Antibacterial Fatty Acids and Related Surfactants.

    PubMed

    Yoon, Bo Kyeong; Jackman, Joshua A; Kim, Min Chul; Cho, Nam-Joon

    2015-09-22

    Medium-chain saturated fatty acids and related compounds (e.g., monoglycerides) represent one class of membrane-active surfactants with antimicrobial properties. Most related studies have been in vitro evaluations of bacterial growth inhibition, and there is limited knowledge about how the compounds in this class destabilize lipid bilayers, which are the purported target within the bacterial cell membrane. Herein, the interaction between three representative compounds in this class and a supported lipid bilayer platform was investigated using quartz crystal microbalance-dissipation and fluorescence microscopy in order to examine membrane destabilization. The three tested compounds were lauric acid, sodium dodecyl sulfate, and glycerol monolaurate. For each compound, we discovered striking differences in the resulting morphological changes of supported lipid bilayers. The experimental trends indicate that the compounds have membrane-disruptive behavior against supported lipid bilayers principally above the respective critical micelle concentration values. The growth inhibition properties of the compounds against standard and methicillin-resistant Staphylococcus aureus bacterial strains were also tested. Taken together, the findings in this work improve our knowledge about how saturated fatty acids and related compounds destabilize lipid bilayers, offering insight into the corresponding molecular mechanisms that lead to membrane morphological responses. PMID:26325618

  10. Spectrum of Membrane Morphological Responses to Antibacterial Fatty Acids and Related Surfactants.

    PubMed

    Yoon, Bo Kyeong; Jackman, Joshua A; Kim, Min Chul; Cho, Nam-Joon

    2015-09-22

    Medium-chain saturated fatty acids and related compounds (e.g., monoglycerides) represent one class of membrane-active surfactants with antimicrobial properties. Most related studies have been in vitro evaluations of bacterial growth inhibition, and there is limited knowledge about how the compounds in this class destabilize lipid bilayers, which are the purported target within the bacterial cell membrane. Herein, the interaction between three representative compounds in this class and a supported lipid bilayer platform was investigated using quartz crystal microbalance-dissipation and fluorescence microscopy in order to examine membrane destabilization. The three tested compounds were lauric acid, sodium dodecyl sulfate, and glycerol monolaurate. For each compound, we discovered striking differences in the resulting morphological changes of supported lipid bilayers. The experimental trends indicate that the compounds have membrane-disruptive behavior against supported lipid bilayers principally above the respective critical micelle concentration values. The growth inhibition properties of the compounds against standard and methicillin-resistant Staphylococcus aureus bacterial strains were also tested. Taken together, the findings in this work improve our knowledge about how saturated fatty acids and related compounds destabilize lipid bilayers, offering insight into the corresponding molecular mechanisms that lead to membrane morphological responses.

  11. Cyclopropanation of membrane unsaturated fatty acids is not essential to the acid stress response of Lactococcus lactis subsp. cremoris.

    PubMed

    To, Thi Mai Huong; Grandvalet, Cosette; Tourdot-Maréchal, Raphaëlle

    2011-05-01

    Cyclopropane fatty acids (CFAs) are synthetized in situ by the transfer of a methylene group from S-adenosyl-L-methionine to a double bond of unsaturated fatty acid chains of membrane phospholipids. This conversion, catalyzed by the Cfa synthase enzyme, occurs in many bacteria and is recognized to play a key role in the adaptation of bacteria in response to a drastic perturbation of the environment. The role of CFAs in the acid tolerance response was investigated in the lactic acid bacterium Lactococcus lactis MG1363. A mutant of the cfa gene was constructed by allelic exchange. The cfa gene encoding the Cfa synthase was cloned and introduced into the mutant to obtain the complemented strain for homologous system studies. Data obtained by gas chromatography (GC) and GC-mass spectrometry (GC-MS) validated that the mutant could not produce CFA. The CFA levels in both the wild-type and complemented strains increased upon their entry to stationary phase, especially with acid-adapted cells or, more surprisingly, with ethanol-adapted cells. The results obtained by performing quantitative reverse transcription-PCR (qRT-PCR) experiments showed that transcription of the cfa gene was highly induced by acidity (by 10-fold with cells grown at pH 5.0) and by ethanol (by 9-fold with cells grown with 6% ethanol) in comparison with that in stationary phase. Cell viability experiments were performed after an acidic shock on the mutant strain, the wild-type strain, and the complemented strain, as a control. The higher viability level of the acid-adapted cells of the three strains after 3 h of shock proved that the cyclopropanation of unsaturated fatty acids is not essential for L. lactis subsp. cremoris survival under acidic conditions. Moreover, fluorescence anisotropy data showed that CFA itself could not maintain the membrane fluidity level, particularly with ethanol-grown cells.

  12. Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity

    NASA Astrophysics Data System (ADS)

    Skedina, M. A.; Katuntsev, V. P.; Buravkova, L. B.; Naidina, V. P.

    Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p < 0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

  13. Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity.

    PubMed

    Skedina, M A; Katuntsev, V P; Buravkova, L B; Naidina, V P

    1998-01-01

    Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p<0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

  14. Tuning aluminum spatial distribution in ZSM-5 membranes: a new strategy to fabricate high performance and stable zeolite membranes for dehydration of acetic acid.

    PubMed

    Yang, Jianhua; Li, Liangqing; Li, Wanze; Wang, Jinqu; Chen, Zan; Yin, Dehong; Lu, Jinming; Zhang, Yan; Guo, Hongchen

    2014-12-01

    A novel ZSM-5 membrane with a low Si/Al ratio and homogeneous aluminum spatial distribution was achieved from an organic template-free inorganic gel in the presence of both OH(-) and F(-) ions and the obtained ZSM-5 membrane exhibited excellent selectivity and high flux and stability for dehydration of acetic acid in a wide AcOH content range.

  15. A novel phosphoric acid doped poly(ethersulphone)-poly(vinyl pyrrolidone) blend membrane for high-temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Xu, Xin; Wang, Haining; Lu, Shanfu; Guo, Zhibin; Rao, Siyuan; Xiu, Ruijie; Xiang, Yan

    2015-07-01

    A high-temperature proton exchange membrane, poly(ethersulphone)-poly(vinyl pyrrolidone) (PES-PVP) blend membrane is successfully prepared by scalable polymer blending method. The physical properties of blend membrane are characterized by DSC, TG and tensile strength test. The DSC and TG results indicate PES-PVP blend membranes possess excellent thermal stability. After phosphoric acid (PA) doping treatment, the blend membrane shows enhanced proton conductivity. PA doping level and volume swelling ratio of the blend membrane are found to be positively related to the PVP content. A high proton conductivity of 0.21 S/cm is achieved at 180 °C for PA doped PES-PVP 80% with a PA doping level of 9.1. PEM fuel cell based on PA doped PES-PVP 80% membrane shows a high power density of 850 mW/cm2 and outstanding stability at 180 °C without extra humidification.

  16. A supported polymeric liquid membrane process for removal of carboxylic acids from a waste stream

    SciTech Connect

    Ho, S.V.

    1999-12-31

    The removal or elimination of organic residues from aqueous waste streams represents a major need in the chemical industry. The authors have developed a new class of membrane called supported polymeric liquid membranes that are capable of removing and concentrating low molecular weight organic compounds from dilute aqueous solutions, especially those that also contain high concentrations of inorganic salts. Attractive features of this membrane process include the ability to recover the contaminants in concentrated form for either recycle or more economical disposal, low pressure (ambient) operation, simple scale-up using commercial hollow fiber modules, and ease of in-situ regeneration of the polymeric liquid. The process has shown treatment feasibility for several types of aqueous waste streams. This paper describes the laboratory development activities for treating a waste stream containing a dilute mixture of C2-C6 carboxylic acids and nitric acid.

  17. Vaccinia extracellular virions enter cells by macropinocytosis and acid-activated membrane rupture

    PubMed Central

    Schmidt, Florian Ingo; Bleck, Christopher Karl Ernst; Helenius, Ari; Mercer, Jason

    2011-01-01

    Vaccinia virus (VACV), the model poxvirus, produces two types of infectious particles: mature virions (MVs) and extracellular virions (EVs). EV particles possess two membranes and therefore require an unusual cellular entry mechanism. By a combination of fluorescence and electron microscopy as well as flow cytometry, we investigated the cellular processes that EVs required to infect HeLa cells. We found that EV particles were endocytosed, and that internalization and infection depended on actin rearrangements, activity of Na+/H+ exchangers, and signalling events typical for the macropinocytic mechanism of endocytosis. To promote their internalization, EVs were capable of actively triggering macropinocytosis. EV infection also required vacuolar acidification, and acid exposure in endocytic vacuoles was needed to disrupt the outer EV membrane. Once exposed, the underlying MV-like particle presumably fused its single membrane with the limiting vacuolar membrane. Release of the viral core into the host cell cytosol allowed for productive infection. PMID:21792173

  18. Vaccinia extracellular virions enter cells by macropinocytosis and acid-activated membrane rupture.

    PubMed

    Schmidt, Florian Ingo; Bleck, Christopher Karl Ernst; Helenius, Ari; Mercer, Jason

    2011-08-31

    Vaccinia virus (VACV), the model poxvirus, produces two types of infectious particles: mature virions (MVs) and extracellular virions (EVs). EV particles possess two membranes and therefore require an unusual cellular entry mechanism. By a combination of fluorescence and electron microscopy as well as flow cytometry, we investigated the cellular processes that EVs required to infect HeLa cells. We found that EV particles were endocytosed, and that internalization and infection depended on actin rearrangements, activity of Na(+)/H(+) exchangers, and signalling events typical for the macropinocytic mechanism of endocytosis. To promote their internalization, EVs were capable of actively triggering macropinocytosis. EV infection also required vacuolar acidification, and acid exposure in endocytic vacuoles was needed to disrupt the outer EV membrane. Once exposed, the underlying MV-like particle presumably fused its single membrane with the limiting vacuolar membrane. Release of the viral core into the host cell cytosol allowed for productive infection. PMID:21792173

  19. Dysferlin regulates cell membrane repair by facilitating injury-triggered acid sphingomyelinase secretion

    PubMed Central

    Defour, A; Van der Meulen, J H; Bhat, R; Bigot, A; Bashir, R; Nagaraju, K; Jaiswal, J K

    2014-01-01

    Dysferlin deficiency compromises the repair of injured muscle, but the underlying cellular mechanism remains elusive. To study this phenomenon, we have developed mouse and human myoblast models for dysferlinopathy. These dysferlinopathic myoblasts undergo normal differentiation but have a deficit in their ability to repair focal injury to their cell membrane. Imaging cells undergoing repair showed that dysferlin-deficit decreased the number of lysosomes present at the cell membrane, resulting in a delay and reduction in injury-triggered lysosomal exocytosis. We find repair of injured cells does not involve formation of intracellular membrane patch through lysosome–lysosome fusion; instead, individual lysosomes fuse with the injured cell membrane, releasing acid sphingomyelinase (ASM). ASM secretion was reduced in injured dysferlinopathic cells, and acute treatment with sphingomyelinase restored the repair ability of dysferlinopathic myoblasts and myofibers. Our results provide the mechanism for dysferlin-mediated repair of skeletal muscle sarcolemma and identify ASM as a potential therapy for dysferlinopathy. PMID:24967968

  20. Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag

    PubMed Central

    Friedrich, Melanie; Setz, Christian; Hahn, Friedrich; Matthaei, Alina; Fraedrich, Kirsten; Rauch, Pia; Henklein, Petra; Traxdorf, Maximilian; Fossen, Torgils; Schubert, Ulrich

    2016-01-01

    The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (l-) domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane. PMID:27120610

  1. POLYCYSTEINE AND OTHER POLYAMINO ACID FUNCTIONALIZED MICROFILTRATION MEMBRANES FOR HEAVY CAPTURE

    EPA Science Inventory

    Polycysteine and other polyamino acid functionalized microfiltration membrane sorbents work exceptionally well for the removal and recovery of toxic heavy metals from aqueous streams. These are high capacity sorbents (0.3-3.7 mg/cm@) with excellent accessibility and selectivity f...

  2. Tuning transport selectivity of ionic species by phosphoric acid gradient in positively charged nanochannel membranes.

    PubMed

    Yang, Meng; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Fan, Xin; Liu, Wei; Liu, Xizhen; Liu, Jianbo; Huang, Jin

    2015-02-01

    The transport of ionic species through a nanochannel plays important roles in fundamental research and practical applications of the nanofluidic device. Here, we demonstrated that ionic transport selectivity of a positively charged nanochannel membrane can be tuned under a phosphoric acid gradient. When phosphoric acid solution and analyte solution were connected by the positively charged nanochannel membrane, the faster-moving analyte through the positively charged nanochannel membrane was the positively charged dye (methylviologen, MV(2+)) instead of the negatively charged dye (1,5-naphthalene disulfonate, NDS(2-)). In other words, a reversed ion selectivity of the nanochannel membranes can be found. It can be explained as a result of the combination of diffusion, induced electroosmosis, and induced electrophoresis. In addition, the influencing factors of transport selectivity, including concentration of phosphoric acid, penetration time, and volume of feed solution, were also investigated. The results showed that the transport selectivity can further be tuned by adjusting these factors. As a method of tuning ionic transport selectivity by establishing phosphoric acid gradient, it will be conducive to improving the separation of ionic species. PMID:25557761

  3. Separation of boric acid in liquid waste with anion exchange membrane contactor

    SciTech Connect

    Park, J.K.; Lee, K.J.

    1995-12-31

    In order to separate boric acid in liquid waste, some possible technologies were investigated and the membrane contactor without dispersion and density differences was selected. The separation experiments on a Celgard 3401{reg_sign} hydrophilic microporous membrane contactor were first performed to obtain the basic data and to determine the properties of the contactor. The experimental conditions were as follows: boric acid concentrations up to 2.0 M, pH 7.0, temperatures of 25 and 55 C, and flow rates of 100, 300, 500, and 800 cm{sup 3}/min. Secondly, an AFN{reg_sign} anion exchange membrane contactor was tested at temperatures of 40 and 55 C and flow rate 400 cm{sup 3}/min. Boric acid solutions were prepared by the same method as that for Celgard 3401{reg_sign} but contained 5.0{times}10{sup {minus}4} M cobalt chloride (CoCl{sub 2}). To simulate membrane contractors, parameters such as the differential diffusion coefficients of boric acid and the mass transfer coefficients in the AFN membrane were measured, and regression models estimating the diffusion coefficient at several conditions were developed. The Celgard 3401{reg_sign} membrane contactor was simulated and compared with experimental data. Simulation results agreed with the experimental data well when a proper correction factor was utilized. The correction factor was independent of the solution temperature and was 8.75 at the flow rates of 300--800 cm{sup 3}/min. This correction factor was also applied to simulate the AFN{reg_sign} resulted in a good agreement with experiment at 40 C, but not 55 C. The retention on cobalt was also better at 40 c than 55 C. The simulating computer program was also applied to a life size contactor designed conceptually.

  4. Membrane lipid composition of pancreatic AR42J cells: modification by exposure to different fatty acids.

    PubMed

    Audi, Nama'a; Mesa, María D; Martínez, María A; Martínez-Victoria, Emilio; Mañas, Mariano; Yago, María D

    2007-04-01

    Dietary fat type influences fatty acids in rat pancreatic membranes, in association with modulation of secretory activity and cell signalling in viable acini. We aimed to confirm whether AR42J cells are a valid model to study the interactions between lipids and pancreatic acinar cell function. For this purpose we have (i) compared the baseline fatty acid composition of AR42J cells with that of pancreatic membranes from rats fed a standard chow; (ii) investigated if fatty acids in AR42J membranes can be modified in culture; and (iii) studied if similar compositional variations that can be evoked in rats when dietary fat type is altered occur in AR42J cells. Weaning Wistar rats were fed for 8 weeks either a commercial chow (C) or semi-purified diets containing virgin olive oil (VOO) or sunflower oil (SO) as fat source. AR42J cells were incubated for 72 hrs in medium containing unmodified fetal calf serum (FCS, AR42J-C cells), FCS enriched with 18:1 n-9 (AR42J-O cells), or FCS enriched with 18:2 n-6 (AR42J-L cells). Fatty acids in crude membranes from rat pancreas and AR42J cells were determined by gas-liquid chromatography. Differences in membrane fatty acids between C rats and AR42J-C cells can be explained in part by variations in the amount of fatty acids in the extracellular environment. Supplementation of FCS with 18:1 n-9 or 18:2 n-6 changed the fatty acid spectrum of AR42J cells in a manner that resembles the pattern found, respectively, in VOO and SO rats, although AR42J-L cells were unable to accumulate 20:4 n-6. The AR42J cell line can be a useful tool to assess the effect of membrane compositional changes on acinar cell function. However, differences in baseline characteristics, and perhaps fatty acid metabolism, indicate that results obtained in AR42J cells should be confirmed with experiments in the whole animal.

  5. Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane.

    PubMed

    Cho, Kwang-Jin; van der Hoeven, Dharini; Zhou, Yong; Maekawa, Masashi; Ma, Xiaoping; Chen, Wei; Fairn, Gregory D; Hancock, John F

    2015-01-01

    K-Ras must localize to the plasma membrane for biological activity; thus, preventing plasma membrane interaction blocks K-Ras signal output. Here we show that inhibition of acid sphingomyelinase (ASM) mislocalizes both the K-Ras isoforms K-Ras4A and K-Ras4B from the plasma membrane to the endomembrane and inhibits their nanoclustering. We found that fendiline, a potent ASM inhibitor, reduces the phosphatidylserine (PtdSer) and cholesterol content of the inner plasma membrane. These lipid changes are causative because supplementation of fendiline-treated cells with exogenous PtdSer rapidly restores K-Ras4A and K-Ras4B plasma membrane binding, nanoclustering, and signal output. Conversely, supplementation with exogenous cholesterol restores K-Ras4A but not K-Ras4B nanoclustering. These experiments reveal different operational pools of PtdSer on the plasma membrane. Inhibition of ASM elevates cellular sphingomyelin and reduces cellular ceramide levels. Concordantly, delivery of recombinant ASM or exogenous ceramide to fendiline-treated cells rapidly relocalizes K-Ras4B and PtdSer to the plasma membrane. K-Ras4B mislocalization is also recapitulated in ASM-deficient Neimann-Pick type A and B fibroblasts. This study identifies sphingomyelin metabolism as an indirect regulator of K-Ras4A and K-Ras4B signaling through the control of PtdSer plasma membrane content. It also demonstrates the critical and selective importance of PtdSer to K-Ras4A and K-Ras4B plasma membrane binding and nanoscale spatial organization. PMID:26572827

  6. Periodontal guided tissue regeneration with a new resorbable polylactic acid membrane.

    PubMed

    Robert, P M; Frank, R M

    1994-05-01

    The aim of the present study was to evaluate the use of 3 types of biodegradable, high molecular weight DL-lactic acid (PLA) membranes containing respectively 0%, 10%, and 30% low molecular weight oligomers for obtaining guided tissue regeneration following treatment of experimental buccal periodontal defects created surgically in 6 young adult beagle dogs. On the buccal aspects of test and control teeth, a mucoperiostal flap was raised and the buccal alveolar bone removed. The exposed root surfaces were scaled and a notch was prepared in the root surface at the level of the reduced crest. PLA membranes containing respectively 0%, 10% and 30% oligomers, drawn at random, were placed over the experimental defects, while no membrane was placed over the control roots. The animals were sacrificed 2, 4, and 6 months after surgery. For comparison between control sites (without membrane) and experimental sites (with 3 types of membrane), serial bucco-lingual sections were made of the experimental and control sites and studied histologically and histometrically. It appeared that a satisfactory regeneration of the periodontal tissues could be obtained with all 3 types of experimental PLA membranes and statistically significant differences could be observed for epithelial attachment, alveolar bone regrowth, connective tissue attachment, and new cementum formation in the experimental group when compared with the controls. All 3 types of membranes were well tolerated. The resorption of the membranes started in the coronal portions and extended progressively in an apical direction and the resorption time seemed to be related to the content of oligomers. PLA membranes could be used as interesting alternatives for GTR in advanced human periodontal lesions.

  7. Acid contact in the rodent pulmonary alveolus causes proinflammatory signaling by membrane pore formation.

    PubMed

    Westphalen, Kristin; Monma, Eiji; Islam, Mohammad N; Bhattacharya, Jahar

    2012-07-01

    Although gastric acid aspiration causes rapid lung inflammation and acute lung injury, the initiating mechanisms are not known. To determine alveolar epithelial responses to acid, we viewed live alveoli of the isolated lung by fluorescence microscopy, then we microinjected the alveoli with HCl at pH of 1.5. The microinjection caused an immediate but transient formation of molecule-scale pores in the apical alveolar membrane, resulting in loss of cytosolic dye. However, the membrane rapidly resealed. There was no cell damage and no further dye loss despite continuous HCl injection. Concomitantly, reactive oxygen species (ROS) increased in the adjacent perialveolar microvascular endothelium in a Ca(2+)-dependent manner. By contrast, ROS did not increase in wild-type mice in which we gave intra-alveolar injections of polyethylene glycol (PEG)-catalase, in mice overexpressing alveolar catalase, or in mice lacking functional NADPH oxidase (Nox2). Together, our findings indicate the presence of an unusual proinflammatory mechanism in which alveolar contact with acid caused membrane pore formation. The effect, although transient, was nevertheless sufficient to induce Ca(2+) entry and Nox2-dependent H(2)O(2) release from the alveolar epithelium. These responses identify alveolar H(2)O(2) release as the signaling mechanism responsible for lung inflammation induced by acid and suggest that intra-alveolar PEG-catalase might be therapeutic in acid-induced lung injury.

  8. Effects of bleomycin and antioxidants on the fatty acid profile of testicular cancer cell membranes.

    PubMed

    Cort, A; Ozben, T; Melchiorre, M; Chatgilialoglu, C; Ferreri, C; Sansone, A

    2016-02-01

    Bleomycin is used in chemotherapy regimens for the treatment of patients having testicular germ-cell tumor (TGCT). There is no study in the literature investigating the effects of bleomycin on membrane lipid profile in testicular cancer cells. We investigated membrane fatty acid (FA) profiles isolated, derivatized and analyzed by gas chromatography of NTera-2 testicular cancer cells incubated with bleomycin (Bleo) for 24 h in the absence and presence of N-Acetyl-L-Cysteine (NAC) and curcumin (Cur) as commonly used antioxidant adjuvants. At the same time the MAPK pathway and EGFR levels were followed up. Bleomycin treatment increased significantly saturated fatty acids (SFA) of phospholipids at the expense of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). Bleomycin also led to a significant increase in the trans lipid isomers of oleic and arachidonic acids due to its free radical producing effect. Incubation with bleomycin increased the p38 MAPK and JNK levels and downregulated EGFR pathway. Coincubation of bleomycin with NAC reversed effects caused by bleomycin. Our results highlight the important role of membrane fatty acid remodeling occurring during the use of bleomycin and its concurrent use with antioxidants which can adjuvate the cytotoxic effects of the chemotherapeutic agents. PMID:26656160

  9. Removal of acetic acid from simulated hemicellulosic hydrolysates by emulsion liquid membrane with organophosphorus extractants.

    PubMed

    Lee, Sang Cheol

    2015-09-01

    Selective removal of acetic acid from simulated hemicellulosic hydrolysates containing xylose and sulfuric acid was attempted in a batch emulsion liquid membrane (ELM) system with organophosphorus extractants. Various experimental variables were used to develop a more energy-efficient ELM process. Total operation time of an ELM run with a very small quantity of trioctylphosphine oxide as the extractant was reduced to about a third of those required to attain almost the same extraction efficiency as obtained in previous ELM works without any extractant. Under specific conditions, acetic acid was selectively separated with a high degree of extraction and insignificant loss of xylose, and its purity and enrichment ratio in the stripping phase were higher than 92% and 6, respectively. Also, reused organic membrane solutions exhibited the extraction efficiency as high as fresh organic solutions did. These results showed that the current ELM process would be quite practical.

  10. Triple-layered PLGA/nanoapatite/lauric acid graded composite membrane for periodontal guided bone regeneration.

    PubMed

    Jamuna-Thevi, Kalitheertha; Saarani, Nur Najiha; Abdul Kadir, Mohamed Rafiq; Hermawan, Hendra

    2014-10-01

    This paper discusses the successful fabrication of a novel triple-layered poly(lactic-co-glycolic acid) (PLGA)-based composite membrane using only a single step that combines the techniques of solvent casting and thermally induced phase separation/solvent leaching. The resulting graded membrane consists of a small pore size layer-1 containing 10 wt% non-stoichiometric nanoapatite (NAp)+1-3 wt% lauric acid (LA) for fibroblastic cell and bacterial inhibition, an intermediate layer-2 with 20-50 wt% NAp+1 wt% LA, and a large pore size layer-3 containing 30-100 wt% NAp without LA to allow bone cell growth. The synergic effects of 10-30 wt% NAp and 1 wt% LA in the membrane demonstrated higher tensile strength (0.61 MPa) and a more elastic behavior (16.1% elongation at break) in 3 wt% LA added membrane compared with the pure PLGA (0.49 MPa, 9.1%). The addition of LA resulted in a remarkable plasticizing effect on PLGA at 3 wt% due to weak intermolecular interactions in PLGA. The pure and composite PLGA membranes had good cell viability toward human skin fibroblast, regardless of LA and NAp contents. PMID:25175212

  11. The lactococcal abortive infection protein AbiP is membrane-anchored and binds nucleic acids.

    PubMed

    Domingues, Susana; McGovern, Stephen; Plochocka, Danuta; Santos, Mário A; Ehrlich, S Dusko; Polard, Patrice; Chopin, Marie-Christine

    2008-03-30

    AbiP, a lactococcal abortive phage infection system, has previously been shown to arrest phage bIL66M1 DNA replication around 10 min after infection and to inhibit the switch off of phage early transcripts. We report here the functional characterization and implication in the abortive infection phenotype of two domains identified in the AbiP sequence. We show that AbiP is a protein anchored to the membrane by an N-terminal membrane-spanning domain. Our results further suggest that membrane localization may be required for the anti-phage activity of AbiP. The remainder of the protein, which contains a putative nucleic acid binding domain, is shown to be located on the cytosolic side. Purified AbiP is shown to bind nucleic acids with an approximately 10-fold preference for RNA relative to ssDNA. AbiP interaction with both ssDNA and RNA molecules occurs in a sequence-independent manner. We have analyzed the effect of substitutions of aromatic and basic residues on the surface of the putative binding fold. In vitro and in vivo studies of these AbiP derivatives indicate that the previously reported effects on phage development might be dependent on the nucleic acid binding activity displayed by the membrane-bound protein.

  12. Eicosapentaenoic acid inhibits glucose-induced membrane cholesterol crystalline domain formation through a potent antioxidant mechanism.

    PubMed

    Mason, R Preston; Jacob, Robert F

    2015-02-01

    Lipid oxidation leads to endothelial dysfunction, inflammation, and foam cell formation during atherogenesis. Glucose also contributes to lipid oxidation and promotes pathologic changes in membrane structural organization, including the development of cholesterol crystalline domains. In this study, we tested the comparative effects of eicosapentaenoic acid (EPA), an omega-3 fatty acid indicated for the treatment of very high triglyceride (TG) levels, and other TG-lowering agents (fenofibrate, niacin, and gemfibrozil) on lipid oxidation in human low-density lipoprotein (LDL) as well as membrane lipid vesicles prepared in the presence of glucose (200 mg/dL). We also examined the antioxidant effects of EPA in combination with atorvastatin o-hydroxy (active) metabolite (ATM). Glucose-induced changes in membrane structural organization were measured using small angle x-ray scattering approaches and correlated with changes in lipid hydroperoxide (LOOH) levels. EPA was found to inhibit LDL oxidation in a dose-dependent manner (1.0-10.0 µM) and was distinguished from the other TG-lowering agents, which had no significant effect as compared to vehicle treatment alone. Similar effects were observed in membrane lipid vesicles exposed to hyperglycemic conditions. The antioxidant activity of EPA, as observed in glucose-treated vesicles, was significantly enhanced in combination with ATM. Glucose treatment produced highly-ordered, membrane-restricted, cholesterol crystalline domains, which correlated with increased LOOH levels. Of the agents tested in this study, only EPA inhibited glucose-induced cholesterol domain formation. These data demonstrate that EPA, at pharmacologic levels, inhibits hyperglycemia-induced changes in membrane lipid structural organization through a potent antioxidant mechanism associated with its distinct, physicochemical interactions with the membrane bilayer. PMID:25449996

  13. Experiments and Modeling of Boric Acid Permeation through Double-Skinned Forward Osmosis Membranes.

    PubMed

    Luo, Lin; Zhou, Zhengzhong; Chung, Tai-Shung; Weber, Martin; Staudt, Claudia; Maletzko, Christian

    2016-07-19

    Boron removal is one of the great challenges in modern wastewater treatment, owing to the unique small size and fast diffusion rate of neutral boric acid molecules. As forward osmosis (FO) membranes with a single selective layer are insufficient to reject boron, double-skinned FO membranes with boron rejection up to 83.9% were specially designed for boron permeation studies. The superior boron rejection properties of double-skinned FO membranes were demonstrated by theoretical calculations, and verified by experiments. The double-skinned FO membrane was fabricated using a sulfonated polyphenylenesulfone (sPPSU) polymer as the hydrophilic substrate and polyamide as the selective layer material via interfacial polymerization on top and bottom surfaces. A strong agreement between experimental data and modeling results validates the membrane design and confirms the success of model prediction. The effects of key parameters on boron rejection, such as boron permeability of both selective layers and structure parameter, were also investigated in-depth with the mathematical modeling. This study may provide insights not only for boron removal from wastewater, but also open up the design of next generation FO membranes to eliminate low-rejection molecules in wider applications.

  14. Reversal of the surface charge asymmetry in purple membrane due to single amino acid substitutions.

    PubMed Central

    Hsu, K C; Rayfield, G W; Needleman, R

    1996-01-01

    Twenty-seven mutant bacteriorhodopsin's were screened to determine the PKa for reversal of the permanent electric dipole moment. The photoelectric response of an aqueous purple-membrane suspension was used to determine the direction of the purple-membrane dipole moment as a function of pH. The pK(a) for the dipole reversal of wild-type bacteriorhodopsin is 4.5. Six of the 27 mutant bacteriorhodopsin's were found to have a pK(a) for dipole reversal larger than that of wild-type bacteriorhodopsin. Two of these mutants, L93T and L93W, involve a neutral amino acid substitution in the interior of the protein. The direction of the purple-membrane permanent electric dipole moment is determined by the purple-membrane surface charge asymmetry. We conclude that these two substitutions, which do not involve charge replacement, alter the pK(a) for the reversal of the purple-membrane surface charge asymmetry. We suggest that these changes to the pK(a) are due to altered protein folding at the surface of the purple-membrane induced by single-site substitutions in the protein interior. PMID:9172760

  15. Experiments and Modeling of Boric Acid Permeation through Double-Skinned Forward Osmosis Membranes.

    PubMed

    Luo, Lin; Zhou, Zhengzhong; Chung, Tai-Shung; Weber, Martin; Staudt, Claudia; Maletzko, Christian

    2016-07-19

    Boron removal is one of the great challenges in modern wastewater treatment, owing to the unique small size and fast diffusion rate of neutral boric acid molecules. As forward osmosis (FO) membranes with a single selective layer are insufficient to reject boron, double-skinned FO membranes with boron rejection up to 83.9% were specially designed for boron permeation studies. The superior boron rejection properties of double-skinned FO membranes were demonstrated by theoretical calculations, and verified by experiments. The double-skinned FO membrane was fabricated using a sulfonated polyphenylenesulfone (sPPSU) polymer as the hydrophilic substrate and polyamide as the selective layer material via interfacial polymerization on top and bottom surfaces. A strong agreement between experimental data and modeling results validates the membrane design and confirms the success of model prediction. The effects of key parameters on boron rejection, such as boron permeability of both selective layers and structure parameter, were also investigated in-depth with the mathematical modeling. This study may provide insights not only for boron removal from wastewater, but also open up the design of next generation FO membranes to eliminate low-rejection molecules in wider applications. PMID:27280490

  16. Double liquid membrane system for the removal of actinides and lanthanides from acidic nuclear wastes

    SciTech Connect

    Chiarizia, R.; Danesi, P.R.

    1987-01-01

    Supported liquid membranes (SLM), consisting of an organic solution of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl-phosphate (TBP) in decalin are able to perform selective separation and concentration of actinide and lanthanide ions from aqueous nitrate feed solutions and synthetic nuclear wastes. In the membrane process a possible strip solution is a mixture of formic acid and hydroxylammonium formate (HAF). The effectiveness of this strip solution is reduced and eventually nullified by the simultaneous transfer through the SLM of HNO3 which accumulates in the strip solution. A possible way to overcome this drawback is to make use of a second SLM consisting of a primary amine which is able to extract only HNO3 from the strip solution. In this work the results obtained by experimentally studying the membrane system: synthetic nuclear waste/CMPO-TBP membrane/HCOOH-HAF strip solution/primary amine membrane/NaOH solution, are reported. They show that the use of a second liquid membrane is effective in controlling the HNO3 concentration in the strip solution, thus allowing the actinide and lanthanide ions removal from the feed solution to proceed to completion.

  17. Use of AC Impedance Analysis to Study Membrane Changes Related to Acid Secretion in Amphibian Gastric Mucosa

    PubMed Central

    Clausen, Chris; Machen, Terry E.; Diamond, Jared M.

    1983-01-01

    We have applied transepithelial AC impedance techniques to gastric mucosa to reconcile ultrastructural and electrophysiological findings about gastric acid secretion and the mucosal barrier. By fitting impedance data measured at different HCl secretion rates to equivalent circuit models, we extracted capacitances and resistances (as measures of membrane area and ionic conductance, respectively) for the apical and basolateral membranes. The impedance measurements were found to be incompatible with earlier equivalent circuit models that modeled membrane electrical properties as lumped circuits based on one or two cell types. A distributed circuit model was developed that assumed only one dominant electrical pathway (i.e., one cell type), but that incorporated electrical effects arising from long and narrow membrane-lined structures present in the epithelium (e.g., gastric crypts, tubulovesicles, lateral intercellular spaces). This morphologically based model was found to represent the measured data accurately, and to yield values for membrane capacitances consistent with morphometric measurements of membrane areas. The main physiological conclusions from this analysis were as follows: (a) The dominant transepithelial current pathway may reside in the oxyntic cells. (b) The transepithelial conductance increase associated with the onset of acid secretion is entirely due to increased conductance of the apical membrane. This is in turn due entirely to increased area of this membrane, resulting from incorporation of tubulovesicular membrane. (c) When membrane conductances are normalized to actual membrane area by use of membrane capacitances, it turns out that acid secretion is not associated with a change in specific ionic conductance (change in conductance per unit area) at either the apical or basolateral membrane. (d) The puzzlingly low value of transepithelial resistance (≤400 Ω-cm2) arises because there are hundreds or thousands of square centimeters of actual

  18. Acid gradient across plasma membrane can drive phosphate bond synthesis in cancer cells: acidic tumor milieu as a potential energy source.

    PubMed

    Dhar, Gautam; Sen, Suvajit; Chaudhuri, Gautam

    2015-01-01

    Aggressive cancers exhibit an efficient conversion of high amounts of glucose to lactate accompanied by acid secretion, a phenomenon popularly known as the Warburg effect. The acidic microenvironment and the alkaline cytosol create a proton-gradient (acid gradient) across the plasma membrane that represents proton-motive energy. Increasing experimental data from physiological relevant models suggest that acid gradient stimulates tumor proliferation, and can also support its energy needs. However, direct biochemical evidence linking extracellular acid gradient to generation of intracellular ATP are missing. In this work, we demonstrate that cancer cells can synthesize significant amounts of phosphate-bonds from phosphate in response to acid gradient across plasma membrane. The noted phenomenon exists in absence of glycolysis and mitochondrial ATP synthesis, and is unique to cancer. Biochemical assays using viable cancer cells, and purified plasma membrane vesicles utilizing radioactive phosphate, confirmed phosphate-bond synthesis from free phosphate (Pi), and also localization of this activity to the plasma membrane. In addition to ATP, predominant formation of pyrophosphate (PPi) from Pi was also observed when plasma membrane vesicles from cancer cells were subjected to trans-membrane acid gradient. Cancer cytosols were found capable of converting PPi to ATP, and also stimulate ATP synthesis from Pi from the vesicles. Acid gradient created through glucose metabolism by cancer cells, as observed in tumors, also proved critical for phosphate-bond synthesis. In brief, these observations reveal a role of acidic tumor milieu as a potential energy source and may offer a novel therapeutic target.

  19. Perfluorosulfonic acid membrane catalysts for optical sensing of anhydrides in the gas phase.

    PubMed

    Ayyadurai, Subasri M; Worrall, Adam D; Bernstein, Jonathan A; Angelopoulos, Anastasios P

    2010-07-15

    Continuous, on-site monitoring of personal exposure levels to occupational chemical hazards in ambient air is a long-standing analytical challenge. Such monitoring is required to institute appropriate health measures but is often limited by the time delays associated with batch air sampling and the need for off-site instrumental analyses. In this work, we report on the first attempt to use the catalytic properties of perfluorosulfonic acid (PSA) membranes to obtain a rapid, selective, and highly sensitive optical response to trimellitic anhydride (TMA) in the gas phase for portable sensor device application. TMA is used as starting material for various organic products and is recognized to be an extremely toxic agent by the National Institute for Occupational Safety and Health (NIOSH). Resorcinol dye is shown to become immobilized in PSA membranes and diffusionally constrain an orange brown product that results from acid-catalyzed reaction with more rapidly diffusing TMA molecules. FTIR, UV/vis, reaction selectivity to TMA versus trimellitic acid (TMLA), and homogeneous synthesis are used to infer 5,7- dihydroxyanthraquinone-2-carboxylic acid as the acylation product of the reaction. The color response has a sensitivity to at least 3 parts per billion (ppb) TMA exposure and, in addition to TMLA, excludes maleic anhydride (MA) and phthalic anhydride (PA). Solvent extraction at long times is used to determine that the resorcinol extinction coefficient in 1100 EW PSA membrane has a value of 1210 m(2)/g at 271.01 nm versus a value of 2010 m(2)/g at 275.22 nm in 50 vol% ethanol/water solution. The hypsochromic wavelength shift and reduced extinction coefficient suggest that the polar perfluorosulfonic acid groups in the membrane provide the thermodynamic driving force for diffusion and immobilization. At a resorcinol concentration of 0.376 g/L in the membrane, a partition coefficient of nearly unity is obtained between the membrane and solution concentrations and a

  20. Advances in Acid Concentration Membrane Technology for the Sulfur-Iodine Thermochemical Cycle

    SciTech Connect

    Frederick F. Stewart; Christopher J. Orme

    2006-11-01

    One of the most promising cycles for the thermochemical generation of hydrogen is the Sulfur-Iodine (S-I) process, where aqueous HI is thermochemically decomposed into H2 and I2 at approximately 350 degrees Celsius. Regeneration of HI is accomplished by the Bunsen reaction (reaction of SO2, water, and iodine to generate H2SO4 and HI). Furthermore, SO2 is regenerated from the decomposition of H2SO4 at 850 degrees Celsius yielding the SO2 as well as O2. Thus, the cycle actually consists of two concurrent oxidation-reduction loops. As HI is regenerated, co-produced H2SO4 must be separated so that each may be decomposed. Current flowsheets employ a large amount (~83 mol% of the entire mixture) of elemental I2 to cause the HI and the H2SO4 to separate into two phases. To aid in the isolation of HI, which is directly decomposed into hydrogen, water and iodine must be removed. Separation of iodine is facilitated by removal of water. Sulfuric acid concentration is also required to facilitate feed recycling to the sulfuric acid decomposer. Decomposition of the sulfuric acid is an equilibrium limited process that leaves a substantial portion of the acid requiring recycle. Distillation of water from sulfuric acid involves significant corrosion issues at the liquid-vapor interface. Thus, it is desirable to concentrate the acid without boiling. Recent efforts at the INL have concentrated on applying pervaporation through Nafion-117, Nafion-112, and sulfonated poly(etheretherketone) (S-PEEK) membranes for the removal of water from HI/water and HI/Iodine/water feedstreams. In pervaporation, a feed is circulated at low pressure across the upstream side of the membrane, while a vacuum is applied downstream. Selected permeants sorb into the membrane, transport through it, and are vaporized from the backside. Thus, a concentration gradient is established, which provides the driving force for transport. In this work, membrane separations have been performed at temperatures as high as

  1. Membrane lipid raft organization is uniquely modified by n-3 polyunsaturated fatty acids

    PubMed Central

    Turk, Harmony F.; Chapkin, Robert S.

    2012-01-01

    Fish oil, enriched in bioactive n-3 polyunsaturated fatty acids (PUFA), has been shown to play a role in prevention of colon cancer. The effects of n-3 PUFA are pleiotropic and multifaceted, resulting in an incomplete understanding of their molecular mechanisms of action. Here, we focus on a highly conserved mechanism of n-3 PUFA, which is the alteration of the organization of the plasma membrane. We highlight recent work demonstrating that enrichment of n-3 PUFA in the plasma membrane alters the lateral organization of membrane signaling assemblies (i.e. lipid rafts). This mechanism is central for n-3 PUFA regulation of downstream signaling, T-cell activation, transcriptional activation, and cytokine secretion. We conclude that these studies provide strong evidence for a predominant mechanism by which n-3 PUFA function in colon cancer prevention. PMID:22515942

  2. Anion carrier formation by calix[4]arene-bis-hydroxymethylphosphonic acid in bilayer membranes.

    PubMed

    Shatursky, Oleg Ya; Kasatkina, Ludmila A; Rodik, Roman V; Cherenok, Sergiy O; Shkrabak, Alexander A; Veklich, Tatiana O; Borisova, Tatiana A; Kosterin, Sergyi O; Kalchenko, Vitaly I

    2014-12-28

    The action of calix[4]arenes C-91, C-97, C-99, C-107 and C-160 on solvent-containing planar bilayer membranes made of cholesterol and egg phosphatidylcholine (egg PC) or synthetic 18-carbon-tail phospholipid DOPC has been investigated in a voltage-clamp mode. Within the range of calix[4]arenes tested, a steady-state voltage-dependent transmembrane current was achieved only after addition of calix[4]-arene C-99 (calix[4]arene-bis-hydroxymethylphosphonic acid) from the side of the membrane the positive potential was applied to. This current exhibited anion selectivity passing more chloride at negative potentials applied from the side of the membrane to which calix[4]arene C-99 was introduced. The kinetics and temperature-dependence determined for calix[4]arene C-99-mediated ionic transport suggest a carrier mode of facilitated diffusion.

  3. Identification of type-2 phosphatidic acid phosphohydrolase (PAPH-2) in neutrophil plasma membranes.

    PubMed

    Boder, E; Taylor, G; Akard, L; Jansen, J; English, D

    1994-11-01

    Plasma membrane phosphatidic acid phosphohydrolase (PAPH) plays an important role in signal transduction by converting phosphatidic acid to diacylglycerol. PAPH-2, a Mg(2+)-independent, detergent-dependent enzyme involved in cellular signal transduction, is reportedly absent from the plasma membranes of neutrophilic leukocytes, a cell that responds to metabolic stimulation with abundant phospholipase D-dependent diacylglycerol generation. The present study was designed to resolve this discrepancy, focusing on the influence of cellular disruption techniques, detergent availability and cation sensitivity on the apparent distribution of PAPH in neutrophil subcellular fractions. The results clearly indicate the presence of two distinct types of PAPH within the particulate and cytosolic fractions of disrupted cells. Unlike the cytosolic enzyme, the particulate enzymes was not potentiated by magnesium and was strongly detergent-dependent. The soluble and particulate enzymes displayed dissimilar pH profiles. Separation of neutrophil particulate material into fractions rich in plasma membranes, specific granules and azurophilic granules by high speed discontinuous density gradient centrifugation revealed that the majority of the particulate activity was confined to plasma membranes. This activity was not inhibited by pretreatment with n-ethyl-maleimide in concentrations as high as 25 mM. PAPH activity recovered in the cytosolic fraction of disrupted neutrophils was almost completely inhibited by 5.0 mM n-ethylmaleimide. We conclude that resting neutrophils possess n-ethylmaleimide-resistant PAPH (type 2) within their plasma membranes. This enzyme may markedly influence the kinetics of cell activation by metabolizing second messengers generated as a result of activation of plasma membrane phospholipase D.

  4. Decreased platelet membrane anisotropy in patients with adrenoleukodystrophy treated with erucic acid (22:1)-rich triglycerides.

    PubMed

    Stöckler, S; Opper, C; Greinacher, A; Hunneman, D H; Korenke, G C; Unkrig, C J; Hanefeld, F

    1997-03-01

    Low platelet count and bleeding diathesis have been observed in patients with adrenoleukodystrophy (ALD) treated with erucic acid (22:1)-rich triglycerides ("Lorenzo's oil'). To investigate possible alterations of biophysical membrane properties, we measured platelet membrane anisotropy, which is inversely related to membrane fluidity, in 16 patients with and in 3 patients without treatment. In patients on treatment, platelet membrane anisotropy was significantly decreased. Additionally, we found increased platelet concentrations of 22:1 and compromised in vitro platelet aggregation response. The decrease of platelet membrane anisotropy is probably a main cause of bleeding diathesis. Long-term haematological side-effects must be considered in ALD patients treated with Lorenzo's oil.

  5. Release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) antimicrobial nanofibrous membranes.

    PubMed

    Jiang, Suwei; Lv, Jian; Ding, Man; Li, Yanan; Wang, Hualin; Jiang, Shaotong

    2016-02-01

    The present work aimed to evaluate the release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) (Tet-CS/PLA) antimicrobial nanofibrous membranes fabricated via electrospinning technique. The electrospinning solution was a blend of Tet, CS formic acid solution and PLA chloroform/ethanol solution. The interaction between CS and PLA in CS/PLA nanofibers was confirmed to be hydrogen bond. The incorporation of Tet caused a slight decrease in the diameter of nanofibers with Tet content below 30%. Tet-CS/PLA nanofibrous membrane showed a slight initial burst within the first 4h before a gradual increase in cumulative release, and the release percentage increased with increasing Tet contents. Tet release (Mt/M∞<0.6) from the medicated nanofibers could be described by Fickian diffusion model and the release profiles showed two sequential stages. Tet-CS/PLA nanofibrous membranes exhibited an effective and sustainable inhabitance on the growth of Staphylococcus aureus, and the antimicrobial activity increased rapidly with increasing Tet contents below 20%. Furthermore, the incorporation of Tet promoted the degradation of nanofibrous membranes.

  6. Release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) antimicrobial nanofibrous membranes.

    PubMed

    Jiang, Suwei; Lv, Jian; Ding, Man; Li, Yanan; Wang, Hualin; Jiang, Shaotong

    2016-02-01

    The present work aimed to evaluate the release behavior of tetracycline hydrochloride loaded chitosan/poly(lactic acid) (Tet-CS/PLA) antimicrobial nanofibrous membranes fabricated via electrospinning technique. The electrospinning solution was a blend of Tet, CS formic acid solution and PLA chloroform/ethanol solution. The interaction between CS and PLA in CS/PLA nanofibers was confirmed to be hydrogen bond. The incorporation of Tet caused a slight decrease in the diameter of nanofibers with Tet content below 30%. Tet-CS/PLA nanofibrous membrane showed a slight initial burst within the first 4h before a gradual increase in cumulative release, and the release percentage increased with increasing Tet contents. Tet release (Mt/M∞<0.6) from the medicated nanofibers could be described by Fickian diffusion model and the release profiles showed two sequential stages. Tet-CS/PLA nanofibrous membranes exhibited an effective and sustainable inhabitance on the growth of Staphylococcus aureus, and the antimicrobial activity increased rapidly with increasing Tet contents below 20%. Furthermore, the incorporation of Tet promoted the degradation of nanofibrous membranes. PMID:26652352

  7. Crystal structure of a membrane-bound l-amino acid deaminase from Proteus vulgaris.

    PubMed

    Ju, Yingchen; Tong, Shuilong; Gao, Yongxiang; Zhao, Wei; Liu, Qi; Gu, Qiong; Xu, Jun; Niu, Liwen; Teng, Maikun; Zhou, Huihao

    2016-09-01

    l-amino acid oxidases/deaminases (LAAOs/LAADs) are a class of oxidoreductases catalyzing the oxidative deamination of l-amino acids to α-keto acids. They are widely distributed in eukaryotic and prokaryotic organisms, and exhibit diverse substrate specificity, post-translational modifications and cellular localization. While LAAOs isolated from snake venom have been extensively characterized, the structures and functions of LAAOs from other species are largely unknown. Here, we reported crystal structure of a bacterial membrane-bound LAAD from Proteus vulgaris (pvLAAD) in complex with flavin adenine dinucleotide (FAD). We found that the overall fold of pvLAAD does not resemble typical LAAOs. Instead it, is similar to d-amino acid oxidases (DAAOs) with an additional hydrophobic insertion module on protein surface. Structural analysis and liposome-binding assays suggested that the hydrophobic module serves as an extra membrane-binding site for LAADs. Bacteria from genera Proteus and Providencia were found to encode two classes of membrane-bound LAADs. Based on our structure, the key roles of residues Q278 and L317 in substrate selectivity were proposed and biochemically analyzed. While LAADs on the membrane were proposed to transfer electrons to respiratory chain for FAD re-oxidization, we observed that the purified pvLAAD could generate a significant amount of hydrogen peroxide in vitro, suggesting it could use dioxygen to directly re-oxidize FADH2 as what typical LAAOs usually do. These findings provide a novel insights for a better understanding this class of enzymes and will help developing biocatalysts for industrial applications. PMID:27422658

  8. Membrane lipid modifications and therapeutic effects mediated by hydroxydocosahexaenoic acid on Alzheimer's disease.

    PubMed

    Torres, Manuel; Price, Samantha L; Fiol-Deroque, Maria A; Marcilla-Etxenike, Amaia; Ahyayauch, Hasna; Barceló-Coblijn, Gwendolyn; Terés, Silvia; Katsouri, Loukia; Ordinas, Margarita; López, David J; Ibarguren, Maitane; Goñi, Félix M; Busquets, Xavier; Vitorica, Javier; Sastre, Magdalena; Escribá, Pablo V

    2014-06-01

    Alzheimer's disease (AD) is a neurodegenerative pathology with relevant unmet therapeutic needs. Both natural aging and AD have been associated with a significant decline in the omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), and accordingly, administration of DHA has been proposed as a possible treatment for this pathology. However, recent clinical trials in mild-to-moderately affected patients have been inconclusive regarding the real efficacy of DHA in halting this disease. Here, we show that the novel hydroxyl-derivative of DHA (2-hydroxydocosahexaenoic acid - OHDHA) has a strong therapeutic potential to treat AD. We demonstrate that OHDHA administration increases DHA levels in the brain of a transgenic mouse model of AD (5xFAD), as well as those of phosphatidylethanolamine (PE) species that carry long polyunsaturated fatty acids (PUFAs). In 5xFAD mice, administration of OHDHA induced lipid modifications that were paralleled with a reduction in amyloid-β (Αβ) accumulation and full recovery of cognitive scores. OHDHA administration also reduced Aβ levels in cellular models of AD, in association with alterations in the subcellular distribution of secretases and reduced Aβ-induced tau protein phosphorylation as well. Furthermore, OHDHA enhanced the survival of neuron-like differentiated cells exposed to different insults, such as oligomeric Aβ and NMDA-mediated neurotoxicity. These results were supported by model membrane studies in which incorporation of OHDHA into lipid-raft-like vesicles was shown to reduce the binding affinity of oligomeric and fibrillar Aβ to membranes. Finally, the OHDHA concentrations used here did not produce relevant toxicity in zebrafish embryos in vivo. In conclusion, we demonstrate the pleitropic effects of OHDHA that might prove beneficial to treat AD, which suggests that an upstream event, probably the modulation of the membrane lipid composition and structure, influences cellular homeostasis reversing the

  9. Binding of small basic peptides to membranes containing acidic lipids: theoretical models and experimental results.

    PubMed Central

    Ben-Tal, N; Honig, B; Peitzsch, R M; Denisov, G; McLaughlin, S

    1996-01-01

    We measured directly the binding of Lys3, Lys5, and Lys7 to vesicles containing acidic phospholipids. When the vesicles contain 33% acidic lipids and the aqueous solution contains 100 mM monovalent salt, the standard Gibbs free energy for the binding of these peptides is 3, 5, and 7 kcal/mol, respectively. The binding energies decrease as the mol% of acidic lipids in the membrane decreases and/or as the salt concentration increases. Several lines of evidence suggest that these hydrophilic peptides do not penetrate the polar headgroup region of the membrane and that the binding is mainly due to electrostatic interactions. To calculate the binding energies from classical electrostatics, we applied the nonlinear Poisson-Boltzmann equation to atomic models of the phospholipid bilayers and the basic peptides in aqueous solution. The electrostatic free energy of interaction, which arises from both a long-range coulombic attraction between the positively charged peptide and the negatively charged lipid bilayer, and a short-range Born or image charge repulsion, is a minimum when approximately 2.5 A (i.e., one layer of water) exists between the van der Waals surfaces of the peptide and the lipid bilayer. The calculated molar association constants, K, agree well with the measured values: K is typically about 10-fold smaller than the experimental value (i.e., a difference of about 1.5 kcal/mol in the free energy of binding). The predicted dependence of K (or the binding free energies) on the ionic strength of the solution, the mol% of acidic lipids in the membrane, and the number of basic residues in the peptide agree very well with the experimental measurements. These calculations are relevant to the membrane binding of a number of important proteins that contain clusters of basic residues. Images FIGURE 2 FIGURE 3 PMID:8842196

  10. The effect of natural and synthetic fatty acids on membrane structure, microdomain organization, cellular functions and human health.

    PubMed

    Ibarguren, Maitane; López, David J; Escribá, Pablo V

    2014-06-01

    This review deals with the effects of synthetic and natural fatty acids on the biophysical properties of membranes, and on their implication on cell function. Natural fatty acids are constituents of more complex lipids, like triacylglycerides or phospholipids, which are used by cells to store and obtain energy, as well as for structural purposes. Accordingly, natural and synthetic fatty acids may modify the structure of the lipid membrane, altering its microdomain organization and other physical properties, and provoking changes in cell signaling. Therefore, by modulating fatty acids it is possible to regulate the structure of the membrane, influencing the cell processes that are reliant on this structure and potentially reverting pathological cell dysfunctions that may provoke cancer, diabetes, hypertension, Alzheimer's and Parkinson's disease. The so-called Membrane Lipid Therapy offers a strategy to regulate the membrane composition through drug administration, potentially reverting pathological processes by re-adapting cell membrane structure. Certain fatty acids and their synthetic derivatives are described here that may potentially be used in such therapies, where the cell membrane itself can be considered as a target to combat disease. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.

  11. Antimicrobial activity of syringic acid against Cronobacter sakazakii and its effect on cell membrane.

    PubMed

    Shi, Chao; Sun, Yi; Zheng, Zhiwei; Zhang, Xiaorong; Song, Kaikuo; Jia, Zhenyu; Chen, Yifei; Yang, Miaochun; Liu, Xin; Dong, Rui; Xia, Xiaodong

    2016-04-15

    Syringic acid (SA) has been reported to exhibit antibacterial ability against various microorganisms, but little work has been done on its effect on Cronobacter sakazakii. In this study, minimum inhibitory concentrations (MICs) of SA against various C. sakazakii strains were determined. Moreover, changes in intracellular ATP concentration, intracellular pH (pHin), membrane potential and membrane integrity were measured to evaluate the influence of SA on cell membrane. Finally, field emission scanning electron microscope (FESEM) was used to assess the morphological changes of bacterial cells caused by SA. It was shown that the MICs of SA against all tested C. sakazakii strains were 5mg/mL. SA retarded bacterial growth, and caused cell membrane dysfunction, which was evidenced by intracellular ATP concentration decrease, pHin reduction, cell membrane hyperpolarization and changes in cellular morphology. These findings indicated that SA has potential to be developed as a natural preservative to control C. sakazakii in foods associated with this pathogen and prevent related infections.

  12. Antagonistic effects of α-tocopherol and ursolic acid on model bacterial membranes.

    PubMed

    Broniatowski, Marcin; Flasiński, Michał; Hąc-Wydro, Katarzyna

    2015-10-01

    α-tocopherol (Toc), the most active component of vitamin E can exert antagonistic effects disabling the therapy of cancers and bacterial infections. Such antagonisms were observed also between Toc and bioactive pentacyclic triterpenes (PT) exhibiting anticancer and antibacterial properties. Both Toc and PT are water-insoluble membrane active substances. Thus, our idea was to emulate their interactions with model Escherichia coli membranes. E. coli inner membranes were selected for the experiments because their lipid composition is quite simple and well characterized and the two main components are phosphatidylethanolamine and phosphatidylglycerol. As a model of E. coli membranes we applied Langmuir monolayers formed by the E. coli total extract of polar lipids (Etotal) as well as by the main lipid components: phosphatidylethanolamine (POPE) and phosphatidylglycerol (ECPG). The antagonistic effects of ursolic acid (Urs) and Toc were investigated with the application of ternary Langmuir monolayers formed by Urs, Toc and one of the phospholipids POPE or ECPG. Our studies indicated that the affinities of Urs and Toc towards the POPE molecule are comparable; whereas there are profound differences in the interactions of Urs and Toc with ECPG. Thus, the model experiments prove that in the case of E. coli membrane, the differences in the interactions between Urs and Toc with the anionic bacterial phosphatidylglycerol can be the key factor responsible for the antagonistic effects observed between PT and Toc in vivo.

  13. Partitioning of amino-acid analogues in a five-slab membrane model

    SciTech Connect

    Sengupta, D; Smith, Jeremy C; Ullmann, G. Matthias

    2008-09-01

    The positional preferences of the twenty amino-acid residues in a phospholipid bilayer are investigated by calculating the solvation free energy of the corresponding side chain analogues using a five-slab continuum electrostatic model. The side-chain analogues of the aromatic residues tryptophan and tyrosine are found to partition in the head-group region, due to compensation between the increase of the non-polar component of the solvation free energy at the boundary with the aqueous region and the decrease in the electrostatic component. The side chain analogue of phenylalanine differs from the other aromatic molecules by being able to partition in both the head-group region and the membrane core. This finding is consistent with experimental findings of the position of phenylalanine in membrane helices. Interestingly, the charged side-chain analogues of arginine and lysine are shown to prefer the head-group region in an orientation that allows the charged moiety to interact with the aqueous layer. The orientation adopted is similar to the 'snorkelling' effect seen in lysine and arginine residues in membrane helices. In contrast, the preference of the charged side-chain analogues of histidine (protonated) and aspartate (deprotonated) for the aqueous layer is shown to be due to a steep decrease in the electrostatic component of the solvation free energy at the boundary to the aqueous region. The calculations allow an understanding of the origins of side chain positioning in membranes and are thus useful in understanding membrane-protein:lipid thermodynamics.

  14. Drug delivery systems using sandwich configurations of electrospun poly(lactic acid) nanofiber membranes and ibuprofen.

    PubMed

    Immich, Ana Paula Serafini; Arias, Manuel Lis; Carreras, Núria; Boemo, Rafael Luís; Tornero, José Antonio

    2013-10-01

    The primary advantages of electrospun membranes include the ability to obtain very thin fibers that are on the order of magnitude of several nanometers with a considerable superficial area and the possibility for these membranes to be manipulated and processed for many different applications. The purpose of this study is to evaluate and quantify the transport mechanisms that control the release of drugs from polymer-based sandwich membranes produced using the electrospinning processes. These electrospun membranes were composed of poly(lactic acid) (PLA) because it is one of the most promising biodegradable polymers due to its mechanical properties, thermoplastic processability and biological properties, such as its biocompatibility and biodegradability. The transport mechanism that controls the drug delivery was evaluated via the release kinetics of a bioactive agent in physiological serum, which was used as a corporal fluid simulation. To describe the delivery process, mathematical models, such as the Power Law, the classical Higuchi equation and an approach to Fick's Second Law were used. Using the applied mathematical models, it is possible to conclude that control over the release of the drug is significantly dependent on the thickness of the membrane rather than the concentration of the drug.

  15. Transport across the outer membrane porin of mycolic acid containing actinomycetales: Nocardia farcinica.

    PubMed

    Singh, Pratik Raj; Bajaj, Harsha; Benz, Roland; Winterhalter, Mathias; Mahendran, Kozhinjampara R

    2015-02-01

    The role of the outer-membrane channel from a mycolic acid containing Gram-positive bacteria Nocardia farcinica, which forms a hydrophilic pathway across the cell wall, was characterized. Single channel electrophysiology measurements and liposome swelling assays revealed the permeation of hydrophilic solutes including sugars, amino acids and antibiotics. The cation selective N. farcinica channel exhibited strong interaction with the positively charged antibiotics; amikacin and kanamycin, and surprisingly also with the negatively charged ertapenem. Voltage dependent kinetics of amikacin and kanamycin interactions were studied to distinguish binding from translocation. Moreover, the importance of charged residues inside the channel was investigated using mutational studies that revealed rate limiting interactions during the permeation.

  16. Analysis of the interactions of sulfur-containing amino acids in membrane proteins.

    PubMed

    Gómez-Tamayo, José C; Cordomí, Arnau; Olivella, Mireia; Mayol, Eduardo; Fourmy, Daniel; Pardo, Leonardo

    2016-08-01

    The interactions of Met and Cys with other amino acid side chains have received little attention, in contrast to aromatic-aromatic, aromatic-aliphatic or/and aliphatic-aliphatic interactions. Precisely, these are the only amino acids that contain a sulfur atom, which is highly polarizable and, thus, likely to participate in strong Van der Waals interactions. Analysis of the interactions present in membrane protein crystal structures, together with the characterization of their strength in small-molecule model systems at the ab-initio level, predicts that Met-Met interactions are stronger than Met-Cys ≈ Met-Phe ≈ Cys-Phe interactions, stronger than Phe-Phe ≈ Phe-Leu interactions, stronger than the Met-Leu interaction, and stronger than Leu-Leu ≈ Cys-Leu interactions. These results show that sulfur-containing amino acids form stronger interactions than aromatic or aliphatic amino acids. Thus, these amino acids may provide additional driving forces for maintaining the 3D structure of membrane proteins and may provide functional specificity.

  17. VOLTAGE CLAMP BEHAVIOR OF IRON-NITRIC ACID SYSTEM AS COMPARED WITH THAT OF NERVE MEMBRANE

    PubMed Central

    Tasaki, I.; Bak, A. F.

    1959-01-01

    The current-voltage relation for the surface layer of an iron wire immersed in nitric acid was investigated by the voltage clamp technique. Comparing the phase of nitric acid to the axoplasm and the metallic phase to the external fluid medium for the nerve fiber, a striking analogy was found between the voltage clamp behavior of the iron-nitric acid system and that of the nerve membrane. The current voltage curve was found to consist of three parts: (a) a straight line representing the behavior of the resting (passive) membrane, (b) a straight line representing the fully excited (active) state, and (c) an intermediate zone connecting (a) and (b). It was shown that in the intermediate zone, the surface of iron consisted of a fully active patch (or patches) surrounded by a remaining resting area. The phenomenon corresponding to "repetitive firing of responses under voltage clamp" in the nerve membrane was demonstrated in the intermediate zone. The behavior of the cobalt electrode system was also investigated by the same technique. An attempt was made to interpret the phenomenon of initiation and abolition of an active potential on the basis of the thermodynamics of irreversible processes. PMID:13654740

  18. Acidic pH promotes oligomerization and membrane insertion of the BclXL apoptotic repressor.

    PubMed

    Bhat, Vikas; Kurouski, Dmitry; Olenick, Max B; McDonald, Caleb B; Mikles, David C; Deegan, Brian J; Seldeen, Kenneth L; Lednev, Igor K; Farooq, Amjad

    2012-12-01

    Solution pH is believed to serve as an intricate regulatory switch in the induction of apoptosis central to embryonic development and cellular homeostasis. Herein, using an array of biophysical techniques, we provide evidence that acidic pH promotes the assembly of BclXL apoptotic repressor into a megadalton oligomer with a plume-like appearance and harboring structural features characteristic of a molten globule. Strikingly, our data reveal that pH tightly modulates not only oligomerization but also ligand binding and membrane insertion of BclXL in a highly subtle manner. Thus, while oligomerization and the accompanying molten globular content of BclXL is least favorable at pH 6, both of these structural features become more pronounced under acidic and alkaline conditions. However, membrane insertion of BclXL appears to be predominantly favored under acidic conditions. In a remarkable contrast, while ligand binding to BclXL optimally occurs at pH 6, it is diminished by an order of magnitude at lower and higher pH. This reciprocal relationship between BclXL oligomerization and ligand binding lends new insights into how pH modulates functional versatility of a key apoptotic regulator and strongly argues that the molten globule may serve as an intermediate primed for membrane insertion in response to apoptotic cues. PMID:22960132

  19. Calcium-triggered membrane interaction of the alpha-synuclein acidic tail.

    PubMed

    Tamamizu-Kato, Shiori; Kosaraju, Malathi G; Kato, Hiroyuki; Raussens, Vincent; Ruysschaert, Jean-Marie; Narayanaswami, Vasanthy

    2006-09-12

    Alpha-synuclein (alpha-syn) is a 140-residue protein that aggregates in intraneuronal inclusions called Lewy bodies in Parkinson's disease (PD). It is composed of an N-terminal domain with a propensity to bind lipids and a C-terminal domain rich in acidic residues (the acidic tail). The objective of this study was to examine the effect of Ca(2+) on the acidic tail conformation in lipid-bound alpha-syn. We exploit the extreme sensitivity of the band III fluorescence emission peak of the pyrene fluorophore to the polarity of its microenvironment to monitor subtle conformational response of the alpha-syn acidic tail to Ca(2+). Using recombinant human alpha-syn bearing a pyrene to probe either the N-terminal domain or the acidic tail, we noted that lipid binding resulted in an increase in band III emission intensity in the pyrene probe tagging the N-terminal domain but not that in the acidic tail. This suggests that the protein is anchored to the lipid surface via the N-terminal domain. However, addition of Ca(2+) caused an increase in band III emission intensity in the pyrene tagging the acidic tail, with a corresponding increased susceptibility to quenching by quenchers located in the lipid milieu, indicative of lipid interaction of this domain. Taken together with the increased beta-sheet content of membrane-associated alpha-syn in the presence of Ca(2+), we propose a model wherein initial lipid interaction occurs via the N-terminal domain, followed by a Ca(2+)-triggered membrane association of the acidic tail as a potential mechanism leading to alpha-syn aggregation. These observations have direct implications in the role of age-related oxidative stress and the attendant cellular Ca(2+) dysregulation as critical factors in alpha-syn aggregation in PD.

  20. Gene characterized for membrane desaturase that produces (E)-11 isomers of mono- and diunsaturated fatty acids.

    PubMed

    Liu, Weitian; Jiao, Hongmei; Murray, Nancy C; O'Connor, Marion; Roelofs, Wendell L

    2002-01-22

    Moth species have evolved integral membrane desaturases that exhibit a wide diversity in substrate specificity, as well as in regiospecificity and stereospecificity of the unsaturated products. We report here the cloning and expression of a single desaturase from the sex pheromone gland of the light brown apple moth, Epiphyas postvittana, that makes E11 isomers of monounsaturated (E11-16 and E11-14) fatty acids and a diunsaturated (E9,E11-14) fatty acid. In the pheromone gland, the monoene precursor is made available by beta oxidation of E11-16 acid with a subsequent two-carbon loss to E9-14 acid. A functional assay using a baculovirus expression system required addition of myristic acid and E9-14 acid precursors to demonstrate the unusual regiospecificity and stereospecificity of this desaturase. The amino acid sequence of this desaturase has approximately 61% identity to that of Z11-desaturases from two other insect species, and only approximately 48% identity to the metabolic Z9-desaturases in those species. A pheromone-gland Z9-desaturase gene also was found with the light brown apple moth that differed in its deduced amino acid sequence (66% identity) with the metabolic Z9-desaturase from fat body in this species. PMID:11805319

  1. Effect of dietary fatty acids on jejunal and ileal oleic acid uptake by rat brush border membrane vesicles.

    PubMed

    Prieto, R M; Stremmel, W; Sales, C; Tur, J A

    1996-04-18

    To test the effect of dietary fatty acids on fatty acid uptake, the influx kinetics of a representative long-chain fatty acid, 3H-oleic acid, in both the jejunum and ileum of rats has been studied using brush border membrane vesicles (BBMV). Animals were fed with semipurified diets containing 5 g fat/100 g diet, as corn oil (control group), safflower oil (unsaturated group) and coconut oil hydrogenated (saturated group). With increasing unbound oleate concentration in the medium, the three dietary groups showed saturable kinetics in both jejunal and ileal BBMV (controls: Vmax = 0.15 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 136 +/- 29.1 nmol for jejunum, and Vmax = 0.23 +/- 0.03 nmol x mg protein-1 x 5 min-1 and Km = 196 +/- 50.3 nmol for ileum; unsaturated: Vmax = 0.28 +/- 0.05 nmol x mg protein-1 x 5 min-1 and Km = 242.7 +/- 91.8 nmol for jejunum, and Vmax = 1.29 +/- 0.06 nmol x mg protein-1 x 5 min-1 and Km = 509.8 +/- 97.5 nmol for ileum; saturated: Vmax = 0.03 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 124.5 +/- 72.6 nmol for jejunum, and Vmax = 0.04 +/- 0.01 nmol x mg protein -1.5 min-1 and Km = 205.6 +/- 85.3 nmol for ileum). These results support the theory that feeding an isocaloric diet containing only unsaturated fatty acids enhanced oleic acid uptake, and feeding an isocaloric diet containing only saturated fatty acids decreased oleic acid uptake. The results obtained in the present work also show the adaptative ability of jejunum and ileum to the type of dietary fat.

  2. ATR-FTIR spectroscopic investigations on the effect of solvents on the permeation of benzoic acid and salicylic acid through silicone membranes.

    PubMed

    Dias, M; Raghavan, S L; Hadgraft, J

    2001-03-23

    The effect of a series of alcohols on the permeation of salicylic acid (SA) and benzoic acid (BA) through silicone membrane was evaluated, using Franz-type diffusion cells. Although permeants were applied at the same thermodynamic activity in all vehicles, the resulting fluxes were found to differ significantly. This was a consequence of the interactions between the vehicles and the membrane. The interactions between the vehicles and the membrane were further investigated using ATR-FTIR spectroscopy. With this technique, it was possible to identify two different diffusion processes when the membrane was pre-treated with buffer, whereas one single diffusion process was observed when the membrane was pre-soaked with the vehicle. The technique was successfully used to deconvolute the relative magnitude of partition and diffusion in the permeation process. It was shown that the permeation of both acids was affected by the effect of the vehicles on the diffusion coefficient and the partition coefficient in the silicone membrane. The solubility of the drug in the impregnated membrane was found to be proportional to the saturated solubility in the vehicle used to treat the membrane. The solubility of BA in the impregnated silicone membrane was twice that of SA.

  3. Within and between breed differences in freezing tolerance and plasma membrane fatty acid composition of boar sperm.

    PubMed

    Waterhouse, K E; Hofmo, P O; Tverdal, A; Miller, R R

    2006-05-01

    The response of sperm to cryopreservation and the fertility of frozen-thawed semen varies between species. Besides species differences in sperm physiology, structure and biochemistry, factors such as sperm transport and female reproductive tract anatomy will affect fertility of frozen-thawed semen. Therefore, studying differences in sperm cryotolerance between breeds and individuals instead of between species may reveal sources of variability in sperm cryotolerance. In the present study, the effect of cooling, re-warming and freezing and thawing on plasma membrane and acrosome integrity of sperm within and between Norwegian Landrace and Duroc breeds was studied. Furthermore, the relation between post-thaw survival rate and fatty acid composition of the sperm plasma membranes was investigated. Flow cytometry assessments of plasma membrane and acrosome integrity revealed no significant differences between breeds; however there were significant male-to-male variations within breeds in post-thaw percentages of live sperm (plasma membrane intact). The most abundant fatty acids in the plasma membranes from both breeds were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1, n-9), docosapentaenoic acid (22:5, n-6) and docosahexaenoic acid (22:6, n-3). The ratio of sigma operator 22:5, n-6 and 22:6, n-3/ sigma operator all other membrane fatty acids was significantly related to survival rate (plasma membrane integrity) of sperm for both Norwegian Landrace (correlation coefficient (r(s)) = 0.64, P < 0.05) and Duroc (r(s) = 0.67, P < 0.05) boars. In conclusion, male-to-male differences in sperm survival rate after freezing and thawing may be partly related to the amount of long-chain polyunsaturated fatty acids in the sperm plasma membranes. PMID:16672353

  4. Energization of amino acid transport in energy-depleted Ehrlich cells and plasma membrane vesicles.

    PubMed

    Ohsawa, M; Kilberg, M S; Kimmel, G; Christensen, H N

    1980-06-20

    We redirect attention to contributions to the energization, of the active transport of amino acids in the Ehrlich cell, beyond the known energization, by down-gradient comigration of Na+, beyond possible direct energization by coupling to ATP breakdown, and beyond known energization by exchange with prior accumulations of amino acids. We re-emphasize the uphill operation of System L, and by prior depletion of cellular amino acids show that this system must receive energy beyond that made available by their coupled exodus. After this depletion the Na+-indepdendent accumulation of the norbornane amino acid, 2-aminobicycloheptane-2-carboxylic acid becomes strongly subject to stimulation by incubation with glucose. Energy transfer between Systems A and L through the mutual substrate action of ordinary amino acids was minimized although not entirely avoided by the use of amino acid analogs specific to each system. When 2,4-dinitrophenol was included in the depleting treatment, and pyruvate, phenazine methosulfate, or glucose used for restoration, recovery of uptake of the norbornane amino acid was independent of external Na+ or K+ levels. Restoration or the uptake of 2-(methylamino)isobutyric acid was, however, decreased by omission of external K+. Contrary to an earlier finding, restoration of uptake of each of these amino acids was associated with distinct and usually correlated rises in cellular ATP levels. ATP addition failed to stimulate exodus of the norbornane amino acid from plasma membrane vesicles, although either NADH or phenazine methosulfate did stimulate exodus. ATP production and use is thus associated with transport energization although evidence for a direct role failed to appear.

  5. Dicarboxylic acids with limited numbers of hydrocarbons stabilize cell membrane and increase osmotic resistance in rat erythrocytes.

    PubMed

    Mineo, Hitoshi; Amita, Nozomi; Kawawake, Megumi; Higuchi, Ayaka

    2013-11-01

    We examined the effect of dicarboxylic acids having 0 to 6 hydrocarbons and their corresponding monocarboxylic or tricarboxylic acids in changing the osmotic fragility (OF) in rat red blood cells (RBCs). Malonic, succinic, glutaric and adipic acids, which are dicarboxylic acids with 1, 2, 3 and 4 straight hydrocarbons located between two carboxylic groups, decreased the OF in a concentration-dependent manner. Other long-chain dicarboxylic acids did not change the OF in rat RBCs. The benzoic acid derivatives, isophthalic and terephthalic acids, but not phthalic acid, decreased the OF in a concentration-dependent manner. Benzene-1,2,3-tricarboxylic acid, but not benzene-1,3,5-tricarboxylic acid, also decreased the OF in rat RBCs. On the other hand, monocarboxylic acids possessing 2 to 7 straight hydrocarbons and benzoic acid increased the OF in rat RBCs. In short-chain dicarboxylic acids, a limited number of hydrocarbons between the two carboxylic groups are thought to form a V- or U-shaped structure and interact with phospholipids in the RBC membrane. In benzene dicarboxylic and tricarboxylic acids, a part of benzene nucleus between the two carboxylic groups is thought to enter the plasma membrane and act on acyl-chain in phospholipids in the RBC membrane. For dicarboxylic and tricarboxylic acids, limited numbers of hydrocarbons in molecules are speculated to enter the RBC membrane with the hydrophilic carboxylic groups remaining outside, stabilizing the structure of the cell membrane and resulting in an increase in osmotic resistance in rat RBCs. PMID:23770357

  6. Fatty acid composition of membrane bilayers: importance of diet polyunsaturated fat balance.

    PubMed

    Abbott, Sarah K; Else, Paul L; Atkins, Taleitha A; Hulbert, A J

    2012-05-01

    In one of the most extensive analyses to date we show that the balance of diet n-3 and n-6 polyunsaturated fatty acids (PUFA) is the most important determinant of membrane composition in the rat under 'normal' conditions. Young adult male Sprague-Dawley rats were fed one of twelve moderate-fat diets (25% of total energy) for 8weeks. Diets differed only in fatty acid (FA) profiles, with saturate (SFA) content ranging 8-88% of total FAs, monounsaturate (MUFA) 6-65%, total PUFA 4-81%, n-6 PUFA 3-70% and n-3 PUFA 1-70%. Diet PUFA included only essential FAs 18:2n-6 and 18:3n-3. Balance between n-3 and n-6 PUFA is defined as the PUFA balance (n-3 PUFA as % of total PUFA) and ranged 1-86% in the diets. FA composition was measured for brain, heart, liver, skeletal muscle, erythrocytes and plasma phospholipids, as well as adipose tissue and plasma triglycerides. The conformer-regulator model was used (slope=1 indicates membrane composition completely conforming to diet). Extensive changes in diet SFA, MUFA and PUFA had minimal effect on membranes (average slopes 0.01, 0.07, 0.07 respectively), but considerable influence on adipose tissue and plasma triglycerides (average slopes 0.27, 0.53, 0.47 respectively). Diet balance between n-3 and n-6 PUFA had a biphasic influence on membrane composition. When n-3 PUFA<10% of total PUFA, membrane composition completely conformed to diet (average slope 0.95), while diet PUFA balance>10% had little influence (average slope 0.19). The modern human diet has an average PUFA balance ~10% and this will likely have significant health implications.

  7. Study and comparison of two enzyme membrane reactors for fatty acids and glycerol production

    SciTech Connect

    Molinari, R.; Santoro, M.E.; Drioli, E. . Dept. of Chemical Engineering and Materials Inst. on Membranes and Chemical Reactors-CNR, Arcavacata di Rende )

    1994-11-01

    Two enzyme membrane reactors (EMR), (1) with one substrate (olive oil) in an oil-in-water emulsion (E-EMR) and (2) with two separated liquid phases (oil and water) (TSLP-EMR), have been studied for the conversion of the triglycerides to fatty acids and glycerol. The enzyme was Candida cylindracea lipase confined on the pressurized face or entrapped in the sponge side of capillary ultrafiltration membranes. Two methods for immobilizing the enzyme in the TSLP-EMR were used: ultrafiltration on a virgin membrane and ultrafiltration on glutaraldehyde pretreated membranes. A multiple use of the reactor was obtained immobilizing the enzyme on the membrane preactivated with glutaraldehyde. The TSLP-EMR showed a specific activity of 0.529 mmol/(mg[center dot]h) versus a specific activity of 0.170 mmol/(mg[center dot]h) of the E-EMR. The rate of fatty acid production in the TSLP-EMR was linear with time showing no enzyme deactivation in an operating time of 80 h. The kinetics observed in the two reactors was different: an equilibrium reaction product-inhibited for the E-EMR and an apparent irreversible reaction of zero order for the TSLP-EMR. Taking into account that in the TSLP-EMR, compared to the E-EMR, (1) the specific activity was higher, (2) the specific rate was constant with the time, and (3) the two products were already separated after the reaction, the TSLP-EMR configuration seems the more convenient.

  8. Membrane protein complexes catalyze both 4- and 3-hydroxylation of cinnamic acid derivatives in monolignol biosynthesis.

    PubMed

    Chen, Hsi-Chuan; Li, Quanzi; Shuford, Christopher M; Liu, Jie; Muddiman, David C; Sederoff, Ronald R; Chiang, Vincent L

    2011-12-27

    The hydroxylation of 4- and 3-ring carbons of cinnamic acid derivatives during monolignol biosynthesis are key steps that determine the structure and properties of lignin. Individual enzymes have been thought to catalyze these reactions. In stem differentiating xylem (SDX) of Populus trichocarpa, two cinnamic acid 4-hydroxylases (PtrC4H1 and PtrC4H2) and a p-coumaroyl ester 3-hydroxylase (PtrC3H3) are the enzymes involved in these reactions. Here we present evidence that these hydroxylases interact, forming heterodimeric (PtrC4H1/C4H2, PtrC4H1/C3H3, and PtrC4H2/C3H3) and heterotrimeric (PtrC4H1/C4H2/C3H3) membrane protein complexes. Enzyme kinetics using yeast recombinant proteins demonstrated that the enzymatic efficiency (V(max)/k(m)) for any of the complexes is 70-6,500 times greater than that of the individual proteins. The highest increase in efficiency was found for the PtrC4H1/C4H2/C3H3-mediated p-coumaroyl ester 3-hydroxylation. Affinity purification-quantitative mass spectrometry, bimolecular fluorescence complementation, chemical cross-linking, and reciprocal coimmunoprecipitation provide further evidence for these multiprotein complexes. The activities of the recombinant and SDX plant proteins demonstrate two protein-complex-mediated 3-hydroxylation paths in monolignol biosynthesis in P. trichocarpa SDX; one converts p-coumaric acid to caffeic acid and the other converts p-coumaroyl shikimic acid to caffeoyl shikimic acid. Cinnamic acid 4-hydroxylation is also mediated by the same protein complexes. These results provide direct evidence for functional involvement of membrane protein complexes in monolignol biosynthesis.

  9. Spontaneous transfer of stearic acids between human serum albumin and PEG:2000-grafted DPPC membranes.

    PubMed

    Pantusa, Manuela; Stirpe, Andrea; Sportelli, Luigi; Bartucci, Rosa

    2010-05-01

    Electron spin resonance (ESR) spectroscopy is used to study the transfer of stearic acids between human serum albumin (HSA) and sterically stabilized liposomes (SSL) composed of dipalmitoylphosphatidylcholine (DPPC) and of submicellar content of poly(ethylene glycol:2000)-dipalmitoylphosphatidylethanolamine (PEG:2000-DPPE). Protein/lipid dispersions are considered in which spin-labelled stearic acids at the 16th carbon atom along the acyl chain (16-SASL) are inserted either in the protein or in the SSL. Two component ESR spectra with different rotational mobility are obtained over a broad range of temperature and membrane composition. Indeed, superimposed to an anisotropic protein-signal, appears a more isotropic lipid-signal. Since in the samples only one matrix (protein or membranes) is spin-labelled, the other component accounts for the transfer of 16-SASL between albumin and membranes. The two components have been resolved and quantified by spectral subtractions, and the fraction, f (p) (16-SASL), of spin labels bound non-covalently to the protein has been used to monitor the transfer. It is found that it depends on the type of donor and acceptor matrix, on the physical state of the membranes and on the grafting density of the polymer-lipids. Indeed, it is favoured from SSL to HSA and the fraction of stearic acids transferred increases with temperature in both directions of transfer. Moreover, in the presence of polymer-lipids, the transfer from HSA to SSL is slightly attenuated, especially in the brush regime of the polymer-chains. Instead, the transfer from SSL to HSA is favoured by the polymer-lipids much more in the mushroom than in the brush regime. PMID:19350232

  10. Unsaturated amino acids derived from isoleucine trigger early membrane effects on plant cells.

    PubMed

    Roblin, Gabriel; Laduranty, Joëlle; Bonmort, Janine; Aidene, Mohand; Chollet, Jean-François

    2016-10-01

    Unsaturated amino acids (UnsAA) have been shown to affect the activity of various biological processes. However, their mode of action has been investigated poorly thus far. We show in this work that 2-amino-3-methyl-4-pentenoic acid (C2) and 2-amino-3-methyl-4-pentynoic acid (C3) structurally derived from isoleucine (Ile) exhibited a multisite action on plant cells. For one, C2 and C3 induced early modifications at the plasma membrane level, as shown by the hyperpolarization monitored by microelectrode implantation in the pulvinar cells of Mimosa pudica, indicating that these compounds are able to modify ionic fluxes. In particular, proton (H(+)) fluxes were modified, as shown by the pH rise monitored in the bathing medium of pulvinar tissues. A component of this effect may be linked to the inhibitory effect observed on the proton pumping and the vanadate-sensitive activity of the plasma membrane H(+)-ATPase monitored in plasma membrane vesicles (PMVs) purified from pulvinar tissues of M. pudica and leaf tissues of Beta vulgaris. This effect may explain, in part, the inhibitory effect of the compounds on the uptake capacity of sucrose and valine by B. vulgaris leaf tissues. In contrast, an unexpected action was observed in cell reactions, implicating ion fluxes and water movement. Indeed, the osmocontractile reactions of pulvini induced either by a mechanical shock in M. pudica or by dark and light signals in Cassia fasciculata were increased, indicating that, compared to Ile, these compounds may modify in a specific way the plasma membrane permeability to water and ions. PMID:27254795

  11. Targeting acidity in diseased tissues: mechanism and applications of the membrane-inserting peptide, pHLIP

    PubMed Central

    Deacon, John; Engelman, Donald M.; Barrera, Francisco N.

    2014-01-01

    pHLIPs are a family of soluble ~36 amino acid peptides, which bind to membrane surfaces. If the environment is acidic, a pHLIP folds and inserts across the membrane to form a stable transmembrane helix, thus preferentially locating itself in acidic tissues. Since tumors and other disease tissues are acidic, pHLIPs’ low-pH targeting behavior leads to applications as carriers for diagnostic and surgical imaging agents. The energy of membrane insertion can also be used to promote the insertion of modestly polar, normally cell-impermeable cargos across the cell membrane into the cytosol of targeted cells, leading to applications in tumor-targeted delivery of therapeutic molecules. We review the biochemical and biophysical basis of pHLIPs’ unique properties, diagnostic and therapeutic applications, and the principles upon which translational applications are being developed. PMID:25444855

  12. Dehydration of multilamellar fatty acid membranes: Towards a computational model of the stratum corneum

    NASA Astrophysics Data System (ADS)

    MacDermaid, Christopher M.; DeVane, Russell H.; Klein, Michael L.; Fiorin, Giacomo

    2014-12-01

    The level of hydration controls the cohesion between apposed lamellae of saturated free fatty acids found in the lipid matrix of stratum corneum, the outermost layer of mammalian skin. This multilamellar lipid matrix is highly impermeable to water and ions, so that the local hydration shell of its fatty acids may not always be in equilibrium with the acidity and relative humidity, which significantly change over a course of days during skin growth. The homeostasis of the stratum corneum at each moment of its growth likely requires a balance between two factors, which affect in opposite ways the diffusion of hydrophilic species through the stratum corneum: (i) an increase in water order as the lipid lamellae come in closer contact, and (ii) a decrease in water order as the fraction of charged fatty acids is lowered by pH. Herein molecular dynamics simulations are employed to estimate the impact of both effects on water molecules confined between lamellae of fatty acids. Under conditions where membrane undulations are energetically favorable, the charged fatty acids are able to sequester cations around points of contact between lamellae that are fully dehydrated, while essentially maintaining a multilamellar structure for the entire system. This observation suggests that the undulations of the fatty acid lamellae control the diffusion of hydrophilic species through the water phase by altering the positional and rotational order of water molecules in the embedded/occluded "droplets."

  13. Model Systems of Precursor Cellular Membranes: Long-Chain Alcohols Stabilize Spontaneously Formed Oleic Acid Vesicles

    PubMed Central

    Rendón, Adela; Carton, David Gil; Sot, Jesús; García-Pacios, Marcos; Montes, Ruth; Valle, Mikel; Arrondo, José-Luis R.; Goñi, Felix M.; Ruiz-Mirazo, Kepa

    2012-01-01

    Oleic acid vesicles have been used as model systems to study the properties of membranes that could be the evolutionary precursors of more complex, stable, and impermeable phospholipid biomembranes. Pure fatty acid vesicles in general show high sensitivity to ionic strength and pH variation, but there is growing evidence that this lack of stability can be counterbalanced through mixtures with other amphiphilic or surfactant compounds. Here, we present a systematic experimental analysis of the oleic acid system and explore the spontaneous formation of vesicles under different conditions, as well as the effects that alcohols and alkanes may have in the process. Our results support the hypothesis that alcohols (in particular 10- to 14-C-atom alcohols) contribute to the stability of oleic acid vesicles under a wider range of experimental conditions. Moreover, studies of mixed oleic-acid-alkane and oleic-acid-alcohol systems using infrared spectroscopy and Langmuir trough measurements indicate that precisely those alcohols that increased vesicle stability also decreased the mobility of oleic acid polar headgroups, as well as the area/molecule of lipid. PMID:22339864

  14. In vitro bioactivity assessment of composite membrane containing antimicrobial lauric acid for guided bone regeneration in dental application

    NASA Astrophysics Data System (ADS)

    Suleiman, Muhammad Jabir; Kalitheertha, Jamuna Thevi; Sabri, Siti Noorzidah

    2015-07-01

    The manuscript reflect research work in fabrication of a triple layered composite membrane and to perform an in vitro bioactivity evaluation on composite membrane containing antimicrobial lauric acid. Poly(lactic-co-glycolic acid) (PLGA) matrix was incorporated with various amounts of nanoapatite (NAp) and lauric acid (LA) to form a triple-layered composite membrane. This membrane was prepared using a single step fabrication technique comprising of solvent casting, thermally induced phase separation and solvent leaching processes. Apatite mineralization was detected on the composite membranes within 30 days of exposure to simulated body fluid (SBF) and showed increased apatite formation at 30-60wt% of NAp content in the PLGA matrix on layer 3 (L3), that has the highest amount of NAp compared with layer 1 (L1) and layer 2 (L2) of the membrane. However, apatite mineralization was not detected on pure PLGA membrane. In addition, incorporation of LA on L1 and L2 has no influence on apatite mineral formation as none detected on these surfaces. The presence of NAp determines the formation of apatite crystals on the composite membrane. These membranes with triple layered design and bioactive properties showed potential use for guided bone regeneration purposes in dental application.

  15. Uptake of barbituric acid derivatives in small intestinal brush border membrane vesicles from retinyl palmitate-treated rats.

    PubMed

    Tanii, H; Horie, T

    2000-08-01

    Brush border membrane was prepared from the small intestinal (jejunum) cells along the crypt-villus axis. The fluorescence spectra of 1,8-anilinonaphthalene sulfonic acid and the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene were measured in the brush border membrane vesicle suspension. The hydrophobicity of brush border membrane was found to be in the order villus tip >mid villus >lower villus. The fluidity of brush border membrane was in the order villus tip acid derivatives by brush border membrane vesicles was well correlated with their partition coefficients (isopentyl acetate/water). No significant difference was observed between the uptake of hexobarbital by brush border membrane vesicles from the villus tip and lower villus. When retinyl palmitate was administered to rats, the fluidity of brush border membrane was found to be higher in the retinyl palmitate-treated rats than in the control rats. However, no significant difference in the uptake of hexobarbital by brush border membrane vesicles was observed between the retinyl palmitate-administered rats and the control rats. Thus, the retinyl palmitate treatment seems unlikely to affect the passively transported ligands like barbituric acid derivatives in brush border membrane vesicles. PMID:10989945

  16. Membrane Stresses Induced by Overproduction of Free Fatty Acids in Escherichia coli.

    SciTech Connect

    Lennen, Rebecca M.; Kruziki, Max A.; Kumar, Kritika; Zinkel, Robert A.; Burnum, Kristin E.; Lipton, Mary S.; Hoover, Spencer W.; Ranatunga, Don Ruwan; Wittkopp, Tyler M.; Marner II, Wesley D.; Pfleger, Brian F.

    2011-11-01

    Microbially produced fatty acids are potential precursors to high energy density biofuels, including alkanes and alkyl ethyl esters by either catalytic conversion of free fatty acids (FFAs) or enzymatic conversions of acyl-acyl carrier protein or acyl-coenzyme A intermediates. Metabolic engineering efforts aimed at overproducing FFAs in Escherichia coli have achieved less than 30% of the maximum theoretical yield on the supplied carbon source. In this work, the viability, morphology, transcript levels, and protein levels of a strain of E. coli that overproduces medium chain length FFAs was compared to an engineered control strain. By early stationary phase, an 85% reduction in viable cell counts and exacerbated loss of inner membrane integrity were observed in the FFA overproducing strain. These effects were enhanced in strains endogenously producing FFAs compared to strains exposed to exogenously fed FFAs. Under two sets of cultivation conditions, long chain unsaturated fatty acid content greatly increased and the expression of genes and proteins required for unsaturated fatty acid biosynthesis were significantly decreased. Membrane stresses were further implicated by increased expression of genes and proteins of the phage shock response, the MarA/Rob/SoxS regulon, and the nuo and cyo operons of aerobic respiration. Gene deletion studies confirmed the importance of the phage shock proteins and Rob for maintaining cell viability, however little to no change in FFA titers was observed after 24 h cultivation. The results of this study serve as a baseline for future targeted attempts to improve FFA yields and titers in E. coli.

  17. Physical Property Requirements of Ion-exchange Polymer Membranes for Acid-base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Roddecha, Supacharee; Thayer, Peter; Jorne', Jacob; Anthamatten, Mitchell

    2013-03-01

    Flow batteries offer feasible solutions to grid-scale storage of intermittent power. We are developing a new type of flow battery that reversibly controls an acid-base neutralization reaction. The battery consists of two highly reversible hydrogen gas electrodes that are exposed to low and high pH process streams. A brine solution runs between the acid and base streams and is separated by cationic and anionic exchange membranes. For both charge and discharge phases, hydrogen gas is produced at one electrode and consumed at the other. During charging, an external potential is applied across the two electrodes to electrochemically produce acid and base from the fed brine solution. Discharge involves electrochemical neutralization of acid and base streams, resulting in current flow through an external load. Several charge and discharge cycles were performed to demonstrate proof of concept. Experiments were conducted to determine the physical property requirements of the ionic exchange polymer layers. Properties including ion conductivity, permselectivity, and membrane stability will be discussed.

  18. Recovery of water and acid from leach solutions using direct contact membrane distillation.

    PubMed

    Kesieme, Uchenna K; Milne, Nicholas; Cheng, Chu Yong; Aral, Hal; Duke, Mikel

    2014-01-01

    This paper describes for the first time the use of direct contact membrane distillation (DCMD) for acid and water recovery from a real leach solution generated by a hydrometallurgical plant. The leach solutions considered contained H2SO4 or HCl. In all tests the temperature of the feed solution was kept at 60 °C. The test work showed that fluxes were within the range of 18-33 kg/m(2)/h and 15-35 kg/m(2)/h for the H2SO4 and HCl systems, respectively. In the H2SO4 leach system, the final concentration of free acid in the sample solution increased on the concentrate side of the DCMD system from 1.04 M up to 4.60 M. The sulfate separation efficiency was over 99.9% and overall water recovery exceeded 80%. In the HCl leach system, HCl vapour passed through the membrane from the feed side to the permeate. The concentration of HCl captured in the permeate was about 1.10 M leaving behind only 0.41 M in the feed from the initial concentration of 2.13 M. In all the experiments, salt rejection was >99.9%. DCMD is clearly viable for high recovery of high quality water and concentrated H2SO4 from spent sulfuric acid leach solution where solvent extraction could then be applied to recover the sulfuric acid and metals. While HCl can be recovered for reuse using only DCMD.

  19. 2-Acrylamido-2-methyl-1-propanesulfonic Acid Grafted Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Acid-/Oxidative-Resistant Cation Exchange for Membrane Electrolysis.

    PubMed

    Pandey, Ravi P; Das, Arindam K; Shahi, Vinod K

    2015-12-30

    For developing acid-/oxidative-resistant aliphatic-polymer-based cation-exchange membrane (CEM), macromolecular modification of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was carried out by controlled chemical grafting of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). To introduce the unsaturation suitable for chemical grafting, dehydrofluorination of commercially available PVDF-co-HFP was achieved under alkaline medium. Sulfonated copolymer (SCP) was prepared by the free radical copolymerization of dehydofluorinated PVDF-co-HFP (DHPVDF-co-HFP) and AMPS in the presence of free radical initiator. Prepared SCP-based CEMs were analyzed for their morphological characteristics, ion-exchange capacity (IEC), water uptake, conductivity, and stabilities (mechanical, chemical, and thermal) in comparison with state-of-art Nafion117 membrane. High bound water content avoids the membrane dehydration, and most optimal (SCP-1.33) membrane exhibited about ∼2.5-fold high bound water content in comparison with that of Nafion117 membrane. Bunsen reaction of iodine-sulfur (I-S) was successfully performed by direct-contact-mode membrane electrolysis in a two-compartment electrolytic cell using different SCP membranes. High current efficiency (83-99%) confirmed absence of any side reaction and 328.05 kJ mol-H2(-1) energy was required for to produce 1 mol of H2 by electrolytic cell with SCP-1.33 membrane. In spite of low conductivity for reported SCP membrane in comparison with that of Nafion117 membrane, SCP-1.33 membrane was assessed as suitable candidate for electrolysis because of its low-cost nature and excellent stabilities in highly acidic environment may be due to partial fluorinated segments in the membrane structure.

  20. 2-Acrylamido-2-methyl-1-propanesulfonic Acid Grafted Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Acid-/Oxidative-Resistant Cation Exchange for Membrane Electrolysis.

    PubMed

    Pandey, Ravi P; Das, Arindam K; Shahi, Vinod K

    2015-12-30

    For developing acid-/oxidative-resistant aliphatic-polymer-based cation-exchange membrane (CEM), macromolecular modification of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was carried out by controlled chemical grafting of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). To introduce the unsaturation suitable for chemical grafting, dehydrofluorination of commercially available PVDF-co-HFP was achieved under alkaline medium. Sulfonated copolymer (SCP) was prepared by the free radical copolymerization of dehydofluorinated PVDF-co-HFP (DHPVDF-co-HFP) and AMPS in the presence of free radical initiator. Prepared SCP-based CEMs were analyzed for their morphological characteristics, ion-exchange capacity (IEC), water uptake, conductivity, and stabilities (mechanical, chemical, and thermal) in comparison with state-of-art Nafion117 membrane. High bound water content avoids the membrane dehydration, and most optimal (SCP-1.33) membrane exhibited about ∼2.5-fold high bound water content in comparison with that of Nafion117 membrane. Bunsen reaction of iodine-sulfur (I-S) was successfully performed by direct-contact-mode membrane electrolysis in a two-compartment electrolytic cell using different SCP membranes. High current efficiency (83-99%) confirmed absence of any side reaction and 328.05 kJ mol-H2(-1) energy was required for to produce 1 mol of H2 by electrolytic cell with SCP-1.33 membrane. In spite of low conductivity for reported SCP membrane in comparison with that of Nafion117 membrane, SCP-1.33 membrane was assessed as suitable candidate for electrolysis because of its low-cost nature and excellent stabilities in highly acidic environment may be due to partial fluorinated segments in the membrane structure. PMID:26642107

  1. Activation of phosphatidic acid metabolism of human erythrocyte membranes by perfringolysin O

    SciTech Connect

    Saito, M.; Ando, S.; Mitsui, K.; Homma, Y.; Takenawa, T.

    1986-05-29

    The effect of perfringolysin O on the lipid metabolism of human erythrocyte membranes was investigated. Erythrocytes were prelabeled with (/sup 3/H)arachidonic acid and (/sup 32/P)inorganic phosphate. In the presence of calcium ion (5.5 mM), the effect of perfringolysin O on lipid metabolism was very similar to that of an calcium-ionophore A23187. In the absence of calcium ion, the accumulation of phosphatidic acid and its following decreasing trend were observed during the reaction with the toxin. Such changes were not caused by filipin. These results suggest that perfringolysin O causes the activation of a diglyceride-phosphatidic acid cycle, which might be involved in the calcium transport.

  2. The effect of acid hydrolysis pretreatment on crystallinity and solubility of kenaf cellulose membrane

    NASA Astrophysics Data System (ADS)

    Saidi, Anis Syuhada Mohd; Zakaria, Sarani; Chia, Chin Hua; Jaafar, Sharifah Nabihah Syed; Padzil, Farah Nadia Mohammad

    2015-09-01

    Cellulose was extracted from kenaf core pulp (KCP) by series of bleaching steps in the sequence (DEED) where D and E are referred as acid and alkali treatment. The bleached kenaf pulp (BKCP) is then pretreated with acid hydrolysis at room temperature for 1 and 3 h respectively. The pretreated cellulose is dissolved in lithium hydroxide/urea (LiOH/urea) and cellulose solution produced was immersed in distilled water bath. BKCP without treatment was also conducted for comparison purpose. The effects of acid hydrolysis pretreatment on solubility and crystallinity are investigated. Higher solubility of cellulose solution is achieved for treated samples. Cellulose II formation and crystallinity index of the cellulose membrane were determined by X-ray diffraction (XRD).

  3. The effect of acid hydrolysis pretreatment on crystallinity and solubility of kenaf cellulose membrane

    SciTech Connect

    Saidi, Anis Syuhada Mohd; Zakaria, Sarani; Chia, Chin Hua; Jaafar, Sharifah Nabihah Syed; Padzil, Farah Nadia Mohammad

    2015-09-25

    Cellulose was extracted from kenaf core pulp (KCP) by series of bleaching steps in the sequence (DEED) where D and E are referred as acid and alkali treatment. The bleached kenaf pulp (BKCP) is then pretreated with acid hydrolysis at room temperature for 1 and 3 h respectively. The pretreated cellulose is dissolved in lithium hydroxide/urea (LiOH/urea) and cellulose solution produced was immersed in distilled water bath. BKCP without treatment was also conducted for comparison purpose. The effects of acid hydrolysis pretreatment on solubility and crystallinity are investigated. Higher solubility of cellulose solution is achieved for treated samples. Cellulose II formation and crystallinity index of the cellulose membrane were determined by X-ray diffraction (XRD)

  4. Sialic Acid Is Required for Neuronal Inhibition by Soluble MAG but not for Membrane Bound MAG

    PubMed Central

    Al-Bashir, Najat; Mellado, Wilfredo; Filbin, Marie T.

    2016-01-01

    Myelin-Associated Glycoprotein (MAG), a major inhibitor of axonal growth, is a member of the immunoglobulin (Ig) super-family. Importantly, MAG (also known as Siglec-4) is a member of the Siglec family of proteins (sialic acid-binding, immunoglobulin-like lectins), MAG binds to complex gangliosides, specifically GD1a and/or GT1b. Therefore, it has been proposed as neuronal receptors for MAG inhibitory effect of axonal growth. Previously, we showed that MAG binds sialic acid through domain 1 at Arg118 and is able to inhibit axonal growth through domain 5. We developed a neurite outgrowth (NOG) assay, in which both wild type MAG and mutated MAG (MAG Arg118) are expressed on cells. In addition we also developed a soluble form NOG in which we utilized soluble MAG-Fc and mutated MAG (Arg118-Fc). Only MAG-Fc is able to inhibit NOG, but not mutated MAG (Arg118)-Fc that has been mutated at its sialic acid binding site. However, both forms of membrane bound MAG- and MAG (Arg118)- expressing cells still inhibit NOG. Here, we review various results from different groups regarding MAG’s inhibition of axonal growth. Also, we propose a model in which the sialic acid binding is not necessary for the inhibition induced by the membrane form of MAG, but it is necessary for the soluble form of MAG. This finding highlights the importance of understanding the different mechanisms by which MAG inhibits NOG in both the soluble fragmented form and the membrane-bound form in myelin debris following CNS damage. PMID:27065798

  5. Rpe65 Isomerase Associates with Membranes through an Electrostatic Interaction with Acidic Phospholipid Headgroups*

    PubMed Central

    Yuan, Quan; Kaylor, Joanna J.; Miu, Anh; Bassilian, Sara; Whitelegge, Julian P.; Travis, Gabriel H.

    2010-01-01

    Opsins are light-sensitive pigments in the vertebrate retina, comprising a G protein-coupled receptor and an 11-cis-retinaldehyde chromophore. Absorption of a photon by an opsin pigment induces isomerization of its chromophore to all-trans-retinaldehyde. After a brief period of activation, opsin releases all-trans-retinaldehyde and becomes insensitive to light. Restoration of light sensitivity to the apo-opsin involves the conversion of all-trans-retinaldehyde back to 11-cis-retinaldehyde via an enzyme pathway called the visual cycle. The critical isomerization step in this pathway is catalyzed by Rpe65. Rpe65 is strongly associated with membranes but contains no membrane-spanning segments. It was previously suggested that the affinity of Rpe65 for membranes is due to palmitoylation of one or more Cys residues. In this study, we re-examined this hypothesis. By two independent strategies involving mass spectrometry, we show that Rpe65 is not palmitoylated nor does it appear to undergo other post-translational modifications at significant stoichiometry. Instead, we show that Rpe65 binds the acidic phospholipids, phosphatidylserine, phosphatidylglycerol, and cardiolipin, but not phosphatidic acid. No binding of Rpe65 to basic phospholipids or neutral lipids was observed. The affinity of Rpe65 to acidic phospholipids was strongly pH-dependent, suggesting an electrostatic interaction of basic residues in Rpe65 with negatively charged phospholipid headgroups. Binding of Rpe65 to liposomes containing phosphatidylserine or phosphatidylglycerol, but not the basic or neutral phospholipids, allowed the enzyme to extract its insoluble substrate, all-trans-retinyl palmitate, from the lipid bilayer for synthesis of 11-cis-retinol. The interaction of Rpe65 with acidic phospholipids is therefore biologically relevant. PMID:19892706

  6. Effect of wheatgrass on membrane fatty acid composition during hepatotoxicity induced by alcohol and heated PUFA.

    PubMed

    Durairaj, Varalakshmi; Shakya, Garima; Pajaniradje, Sankar; Rajagopalan, Rukkumani

    2014-06-01

    Alcoholism is a broad term used for problems related to alcohol, medically considered as disease, specifically an addictive illness, abuse, and dependence. It is the major cause of liver disease in western countries. Alcoholic liver disease encompasses the hepatic alterations leading to fatty liver, hepatitis, and fibrosis or cirrhosis. Fried food items prepared with repeatedly heated polyunsaturated fatty acid (PUFA) exacerbate the disturbances induced by alcohol. The use of herbs to treat diseases is almost universal. Wheatgrass (WG) is used as a supplemental nutrition because of its unique curative properties. As it has antioxidant property, it prevents cancer, diabetes, and acts as liver cleanser. The present study was undertaken to evaluate the efficacy of WG on preserving membrane integrity in liver damage induced by alcohol and heated PUFA (ΔPUFA).The rats were divided into four groups. The animals in group 1 served as normal (standard diet), group 2 served as hepatotoxic (alcohol + ΔPUFA), group 3 served as treated (alcohol + ΔPUFA + WG), and group 4 served as WG control. The compositions of membrane fatty acid, total phospholipids, phospholipase A, C (PLA and PLC) were analyzed in liver to evaluate the effects of WG. Changes in fatty acid composition, decrease in phospholipids levels, and increase in PLA, PLC were observed in the diseased group. Restoration effect was seen in WG-treated rats. Histopathological observations were in correlation with the biochemical parameters. From the results obtained, we conclude that WG effectively protects the liver against alcohol and ΔPUFA-induced changes in fatty acid composition and preserves membrane integrity. PMID:24706101

  7. Membrane-Inspired Acidically Stable Dye-Sensitized Photocathode for Solar Fuel Production.

    PubMed

    Click, Kevin A; Beauchamp, Damian R; Huang, Zhongjie; Chen, Weilin; Wu, Yiying

    2016-02-01

    Tandem dye-sensitized photoelectrochemical cells (DSPECs) for water splitting are a promising method for sustainable energy conversion but so far have been limited by their lack of aqueous stability and photocurrent mismatch between the cathode and anode. In nature, membrane-enabled subcellular compartmentation is a general approach to control local chemical environments in the cell. The hydrophobic tails of the lipid make the bilayer impermeable to ions and hydrophilic molecules. Herein we report the use of an organic donor-acceptor dye that prevents both dye desorption and semiconductor degradation by mimicking the hydrophobic/hydrophilic properties of lipid bilayer membranes. The dual-functional photosensitizer (denoted as BH4) allows for efficient light harvesting while also protecting the semiconductor surface from protons and water via its hydrophobic π linker. The protection afforded by this membrane-mimicking dye gives this system excellent stability in extremely acidic (pH 0) conditions. The acidic stability also allows for the use of cubane molybdenum-sulfide cluster as the hydrogen evolution reaction (HER) catalyst. This system produces a proton-reducing current of 183 ± 36 μA/cm(2) (0 V vs NHE with 300 W Xe lamp) for an unprecedented 16 h with no degradation. These results introduce a method for developing high-current, low-pH DSPECs and are a significant move toward practical dye-sensitized solar fuel production. PMID:26744766

  8. Fatty acids production from hydrogen and carbon dioxide by mixed culture in the membrane biofilm reactor.

    PubMed

    Zhang, Fang; Ding, Jing; Zhang, Yan; Chen, Man; Ding, Zhao-Wei; van Loosdrecht, Mark C M; Zeng, Raymond J

    2013-10-15

    Gasification of waste to syngas (H2/CO2) is seen as a promising route to a circular economy. Biological conversion of the gaseous compounds into a liquid fuel or chemical, preferably medium chain fatty acids (caproate and caprylate) is an attractive concept. This study for the first time demonstrated in-situ production of medium chain fatty acids from H2 and CO2 in a hollow-fiber membrane biofilm reactor by mixed microbial culture. The hydrogen was for 100% utilized within the biofilms attached on the outer surface of the hollow-fiber membrane. The obtained concentrations of acetate, butyrate, caproate and caprylate were 7.4, 1.8, 0.98 and 0.42 g/L, respectively. The biomass specific production rate of caproate (31.4 mmol-C/(L day g-biomass)) was similar to literature reports for suspended cell cultures while for caprylate the rate (19.1 mmol-C/(L day g-biomass)) was more than 6 times higher. Microbial community analysis showed the biofilms were dominated by Clostridium spp., such as Clostridium ljungdahlii and Clostridium kluyveri. This study demonstrates a potential technology for syngas fermentation in the hollow-fiber membrane biofilm reactors.

  9. Membrane-Inspired Acidically Stable Dye-Sensitized Photocathode for Solar Fuel Production.

    PubMed

    Click, Kevin A; Beauchamp, Damian R; Huang, Zhongjie; Chen, Weilin; Wu, Yiying

    2016-02-01

    Tandem dye-sensitized photoelectrochemical cells (DSPECs) for water splitting are a promising method for sustainable energy conversion but so far have been limited by their lack of aqueous stability and photocurrent mismatch between the cathode and anode. In nature, membrane-enabled subcellular compartmentation is a general approach to control local chemical environments in the cell. The hydrophobic tails of the lipid make the bilayer impermeable to ions and hydrophilic molecules. Herein we report the use of an organic donor-acceptor dye that prevents both dye desorption and semiconductor degradation by mimicking the hydrophobic/hydrophilic properties of lipid bilayer membranes. The dual-functional photosensitizer (denoted as BH4) allows for efficient light harvesting while also protecting the semiconductor surface from protons and water via its hydrophobic π linker. The protection afforded by this membrane-mimicking dye gives this system excellent stability in extremely acidic (pH 0) conditions. The acidic stability also allows for the use of cubane molybdenum-sulfide cluster as the hydrogen evolution reaction (HER) catalyst. This system produces a proton-reducing current of 183 ± 36 μA/cm(2) (0 V vs NHE with 300 W Xe lamp) for an unprecedented 16 h with no degradation. These results introduce a method for developing high-current, low-pH DSPECs and are a significant move toward practical dye-sensitized solar fuel production.

  10. Copoly(arlene ether)s containing pendant sulfonic acid groups as proton exchange membrane

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik; Robertson, Gilles; Guiver, Michael

    2008-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The P AE and PAEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2-phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. The sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sP AE and sP AEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (DS) of 1.0 had high ion exchange capacities (IEC{sub v}(wet) (volume-based, wet state)) of 1.77 and 2.55 meq./cm{sup 3}, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5-51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the area of outstanding properties in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based). Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  11. Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water.

    PubMed

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2016-03-01

    This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO₂ concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO₂ photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO₂ particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst.

  12. Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water.

    PubMed

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2016-01-01

    This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO₂ concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO₂ photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO₂ particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst. PMID:26938568

  13. Effect of glycyrrhetinic acid on membrane band 3 in human erythrocytes.

    PubMed

    Fiore, Cristina; Bordin, Luciana; Pellati, Donatella; Armanini, Decio; Clari, Giulio

    2008-11-01

    Glycyrrhetinic acid (GA) is a hydrolytic product of the triterpene glycoside of glycyrrhizic acid, one of the main constituents of licorice root, which has long been studied, due to its several biological and endocrine properties. In this paper, GA was tested on human erythrocytes, and GA-induced alterations were compared with those caused by diamide, a mild oxidant inducing well-characterized cell/membrane alterations, and n-ethylmaleimide (NEM), as alkylating agent. In order to verify the biochemical steps underlying the action of GA, band 3 Tyr-phosphorylation level, enzyme recruitment and band 3 clustering in cells pre-incubated with GA before diamide treatment were all examined. Results show that GA, in a dose-dependent manner, prevents both diamide and NEM-induced band 3 Tyr-phosphorylation, but not GSH decrease caused by both compounds. In addition, diamide-induced band 3 clustering and IgG binding to altered cells were also completely reversed by GA pre-treatment. Also, when membrane sensitivity toward proteolytic digestion was tested, GA-treated cells showed high resistance to proteolysis. In conclusion, in human erythrocytes, GA is proposed to strengthen membrane integrity against both oxidative and proteolytic damage. PMID:18778682

  14. The fusogenic lipid phosphatidic acid promotes the biogenesis of mitochondrial outer membrane protein Ugo1

    PubMed Central

    Keller, Michael; Taskin, Asli A.; Horvath, Susanne E.; Guan, Xue Li; Prinz, Claudia; Opalińska, Magdalena; Zorzin, Carina; van der Laan, Martin; Wenk, Markus R.; Schubert, Rolf; Wiedemann, Nils; Holzer, Martin

    2015-01-01

    Import and assembly of mitochondrial proteins depend on a complex interplay of proteinaceous translocation machineries. The role of lipids in this process has been studied only marginally and so far no direct role for a specific lipid in mitochondrial protein biogenesis has been shown. Here we analyzed a potential role of phosphatidic acid (PA) in biogenesis of mitochondrial proteins in Saccharomyces cerevisiae. In vivo remodeling of the mitochondrial lipid composition by lithocholic acid treatment or by ablation of the lipid transport protein Ups1, both leading to an increase of mitochondrial PA levels, specifically stimulated the biogenesis of the outer membrane protein Ugo1, a component of the mitochondrial fusion machinery. We reconstituted the import and assembly pathway of Ugo1 in protein-free liposomes, mimicking the outer membrane phospholipid composition, and found a direct dependency of Ugo1 biogenesis on PA. Thus, PA represents the first lipid that is directly involved in the biogenesis pathway of a mitochondrial membrane protein. PMID:26347140

  15. Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water

    PubMed Central

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2016-01-01

    This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO2 concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO2 photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO2 particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst. PMID:26938568

  16. Differential stability of photosynthetic membranes and fatty acid composition at elevated temperature in Symbiodinium

    NASA Astrophysics Data System (ADS)

    Díaz-Almeyda, E.; Thomé, P. E.; El Hafidi, M.; Iglesias-Prieto, R.

    2011-03-01

    Coral reefs are threatened by increasing surface seawater temperatures resulting from climate change. Reef-building corals symbiotic with dinoflagellates in the genus Symbiodinium experience dramatic reductions in algal densities when exposed to temperatures above the long-term local summer average, leading to a phenomenon called coral bleaching. Although the temperature-dependent loss in photosynthetic function of the algal symbionts has been widely recognized as one of the early events leading to coral bleaching, there is considerable debate regarding the actual damage site. We have tested the relative thermal stability and composition of membranes in Symbiodinium exposed to high temperature. Our results show that melting curves of photosynthetic membranes from different symbiotic dinoflagellates substantiate a species-specific sensitivity to high temperature, while variations in fatty acid composition under high temperature rather suggest a complex process in which various modifications in lipid composition may be involved. Our results do not support the role of unsaturation of fatty acids of the thylakoid membrane as being mechanistically involved in bleaching nor as being a dependable tool for the diagnosis of thermal susceptibility of symbiotic reef corals.

  17. Altered erythrocyte membrane fatty acid profile in typical Rett syndrome: effects of omega-3 polyunsaturated fatty acid supplementation.

    PubMed

    Signorini, Cinzia; De Felice, Claudio; Leoncini, Silvia; Durand, Thierry; Galano, Jean-Marie; Cortelazzo, Alessio; Zollo, Gloria; Guerranti, Roberto; Gonnelli, Stefano; Caffarelli, Carla; Rossi, Marcello; Pecorelli, Alessandra; Valacchi, Giuseppe; Ciccoli, Lucia; Hayek, Joussef

    2014-11-01

    This study mainly aims at examining the erythrocyte membrane fatty acid (FAs) profile in Rett syndrome (RTT), a genetically determined neurodevelopmental disease. Early reports suggest a beneficial effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on disease severity in RTT. A total of 24 RTT patients were assigned to ω-3 PUFAs-containing fish oil for 12 months in a randomized controlled study (average DHA and EPA doses of 72.9, and 117.1mg/kgb.w./day, respectively). A distinctly altered FAs profile was detectable in RTT, with deficient ω-6 PUFAs, increased saturated FAs and reduced trans 20:4 FAs. FAs changes were found to be related to redox imbalance, subclinical inflammation, and decreased bone density. Supplementation with ω-3 PUFAs led to improved ω-6/ω-3 ratio and serum plasma lipid profile, decreased PUFAs peroxidation end-products, normalization of biochemical markers of inflammation, and reduction of bone hypodensity as compared to the untreated RTT group. Our data indicate that a significant FAs abnormality is detectable in the RTT erythrocyte membranes and is partially rescued by ω-3 PUFAs.

  18. Porous bead-on-string poly(lactic acid) fibrous membranes for air filtration.

    PubMed

    Wang, Zhe; Zhao, Chuchu; Pan, Zhijuan

    2015-03-01

    Porous bead-on-string poly(lactic acid) (PLA) nanofibrous membranes (NMs) were fabricated by electrospinning, and the formation mechanism of the membranes was determined in this study. The PLA fibrous morphology, including the fiber diameter, bead size, number of beads, and surface structure of the beads, could be closely controlled by regulating the solvent compositions and the concentrations of the PLA solutions. The filtration performance, which was evaluated by measuring the penetration of sodium chloride (NaCl) aerosol particles with an average diameter of 260nm, indicated that the filtration efficiency and pressure drop for the resultant PLA membranes could be manipulated by modifying the morphology of the fibers. Moderate bead size and quantity contribute to the low pressure drop, and small fiber diameters and nanopores on the beads were conducive to high filtration efficiency. Furthermore, the NM formed from a 5 wt% solution and a solvent mixture containing dichloromethane (DCM)/N,N-dimethylacetamide (DMAC) in a 10/1 ratio of PLA by weight exhibited excellent filtration efficiency (99.997%) and a low pressure drop (165.3 Pa), which are promising characteristics for the membranes' application as filters for respiratory protection, indoor air purification, and other filtration applications. PMID:25499733

  19. Polyunsaturated fatty acids and membrane organization: The balance between immunotherapy and susceptibility to infection

    PubMed Central

    Shaikh, Saame Raza; Edidin, Michael

    2008-01-01

    Polyunsaturated fatty acids (PUFAs), notably of the n-3 series, have immunosuppressive effects which make these molecules candidates for treating inflammatory symptoms associated with cardiovascular disease, obesity, arthritis, and asthma. However, immunosuppression by PUFAs could increase susceptibility to bacterial and viral infection. A detailed molecular picture is required in order to understand the balance between the benefits and risks of utilizing PUFAs as adjuvant immunosuppressants. Here we review evidence that incorporation of PUFAs into membrane lipids of antigen-presenting cells (APCs) downregulates APC function. We propose that PUFAs modulate antigen presentation by altering the organization of lipid and protein molecules of the plasma membrane and endomembranes; this alters recognition and responses by T cells. The foundation of our hypothesis is built on data from artificial bilayer experiments which provide the physical principles by which PUFA acyl chains affect membrane architecture. This review also reconciles conflicting results in the literature by discussing the advantages and disadvantages of differing methods of PUFA treatment of cells. We suggest that membrane modulation of immune cells may be an important and overlooked mechanism of immunomodulation. In addition, we propose that mechanistic studies with defined experimental protocols will speed the translation of laboratory studies on PUFAs to the clinic. PMID:18346461

  20. Porous bead-on-string poly(lactic acid) fibrous membranes for air filtration.

    PubMed

    Wang, Zhe; Zhao, Chuchu; Pan, Zhijuan

    2015-03-01

    Porous bead-on-string poly(lactic acid) (PLA) nanofibrous membranes (NMs) were fabricated by electrospinning, and the formation mechanism of the membranes was determined in this study. The PLA fibrous morphology, including the fiber diameter, bead size, number of beads, and surface structure of the beads, could be closely controlled by regulating the solvent compositions and the concentrations of the PLA solutions. The filtration performance, which was evaluated by measuring the penetration of sodium chloride (NaCl) aerosol particles with an average diameter of 260nm, indicated that the filtration efficiency and pressure drop for the resultant PLA membranes could be manipulated by modifying the morphology of the fibers. Moderate bead size and quantity contribute to the low pressure drop, and small fiber diameters and nanopores on the beads were conducive to high filtration efficiency. Furthermore, the NM formed from a 5 wt% solution and a solvent mixture containing dichloromethane (DCM)/N,N-dimethylacetamide (DMAC) in a 10/1 ratio of PLA by weight exhibited excellent filtration efficiency (99.997%) and a low pressure drop (165.3 Pa), which are promising characteristics for the membranes' application as filters for respiratory protection, indoor air purification, and other filtration applications.

  1. Comparison of clinical outcomes following guided tissue regeneration treatment with a polylactic acid barrier or a collagen membrane.

    PubMed

    Wu, Shih-Yun; Chen, Yen-Ting; Chen, Chi-Wei; Chi, Lin-Yang; Hsu, Nai-Ying; Hung, Shan-Ling; Ling, Li-Jane

    2010-04-01

    This prospective, randomized, controlled clinical trial compared the clinical outcomes for a polylactic acid barrier versus a collagen membrane in conjunction with guided tissue regeneration (GTR). Thirty patients with chronic periodontitis and at least one intrabony defect of a minimum 4 mm were enrolled. Following full-mouth scaling, GTR using a collagen membrane or a polylactic acid barrier was performed at one site in each patient. At 1 week before and 6 months after surgery, probing pocket depth (PPD), clinical attachment level (CAL), marginal tissue recession, and bone fill were assessed. A significant reduction in PPD (2.50 +/- 1.35 mm for the polylactic acid barrier and 2.60 +/- 1.08 mm for the collagen membrane) was obtained, in addition to gains in CAL (2.40 +/- 1.17 mm for the polylactic acid barrier and 2.60 +/- 1.26 mm for the collagen membrane) and bone fill (0.33 +/- 1.89 mm for polylactic acid barrier and 2.57 +/- 1.64 mm for collagen membrane), for each group compared to baseline. Significantly, the results from 6 months after surgery showed that there was greater bone fill when the collagen membrane was used compared to the polylactic acid barrier.

  2. OST alpha-OST beta: a key membrane transporter of bile acids and conjugated steroids.

    PubMed

    Ballatori, Nazzareno; Li, Na; Fang, Fang; Boyer, James L; Christian, Whitney V; Hammond, Christine L

    2009-01-01

    The organic solute and steroid transporter, Ost alpha-Ost beta, is an unusual heteromeric carrier that appears to play a central role in the transport of bile acids, conjugated steroids, and structurally-related molecules across the basolateral membrane of many epithelial cells. The transporter's substrate specificity, transport mechanism, tissue distribution, subcellular localization, transcriptional regulation, as well as the phenotype of the recently characterized Ost alpha-deficient mice all strongly support this model. In particular, the Ost alpha-deficient mice display a marked defect in intestinal bile acid and conjugated steroid absorption; a decrease in bile acid pool size and serum bile acid levels; altered intestinal, hepatic and renal disposition of known substrates of the transporter; and altered serum triglyceride, cholesterol, and glucose levels. Collectively, the data indicate that Ost alpha-Ost beta is essential for bile acid and sterol disposition, and suggest that the carrier may be involved in human conditions related to imbalances in bile acid or lipid homeostasis.

  3. Free fatty acids as a major component of the chlorosulfolipid membrane of Ochromonas danica

    SciTech Connect

    Winicov, I.

    1985-01-01

    This work is an attempt to determine whether or not free fatty acids are components of the natural membrane of Ochromonas danica. If the FFAs were artifacts, they would most likely have been produced during solvent extraction or during the procedure for flagellar detachment. Attempts to denature putative solvent-activated lipase(s) through exposure to boiling isopropanol or by crosslinking the flagella with glutaraldehyde prior to extraction failed to eliminate the free fatty acid fraction, nor to significantly alter its composition. Exposure of flagella to albumin resulted in the net transfer of FFAs to the supernatant phase, showing their presence is not caused by solvent activated lipolysis. Finally levels of labelled free fatty acids failed to rise as a function of time after deflagellation in cells grown in the presence of (10-/sup 14/C)-oleic acid. Acid hydrolysis of the total labelled lipid at elevated temperature increased the percentage of counts occurring as unesterified fatty acids (from 2.6% to 64.8%). This, taken together with a corresponding loss of the more polar labelled material (66.8% to 8.2%) indicates that some esterified lipids were present, but probably not broken down during the isolation procedure.

  4. Effect of hydrofluoric acid (HF) concentration to pores size diameter of silicon membrane.

    PubMed

    Burham, Norhafizah; Hamzah, Azrul Azlan; Majlis, Burhanuddin Yeop

    2014-01-01

    This paper studies parameters which affect the pore size diameter of a silicon membrane. Electrochemical etching is performed in characterise the parameter involved in this process. The parameter has been studied is volume ratio of hydrofluoric acid (HF) and ethanol as an electrolyte aqueous for electrochemical etch. This electrolyte aqueous solution has been mixed between HF and ethanol with volume ratio 3:7, 5:5, 7:3 and 9:1. As a result, the higher volume of HF in this electrolyte gives the smallest pore size diameter compared to the lower volume of HF. These samples have been dipped into HF and ethanol electrolyte aqueous with supplied 25 mA/cm2 current density for 20, 30, 40, and 50 minutes. The samples will inspect under Scanning Electron Microscope (SEM) to execute the pore formations on silicon membrane surface.

  5. Interaction of 2,4-dichlorophenoxyacetic acid (2,4-D) with cell and model membranes.

    PubMed

    Suwalsky, M; Benites, M; Villena, F; Aguilar, F; Sotomayor, C P

    1996-12-01

    2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide, is a component of the "agent orange' whose toxicity has been extensively studied without definite conclusions. In order to evaluate its perturbing effect upon cell membranes, 2,4-D was made to interact with human erythrocytes and molecular models. These studies were performed by scanning electron microscopy on red cells, fluorescence spectroscopy on dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles and X-ray diffraction on multilayers of DMPC and dimyristoylphosphatidylethanolamine (DMPE). It was observed that 2,4-D induced a pronounced shape change to the erythrocytes. This effect is explained by the herbicide interaction with the outer monolayer of the red cell membrane. PMID:8972711

  6. Antibacterial Activity of Shikimic Acid from Pine Needles of Cedrus deodara against Staphylococcus aureus through Damage to Cell Membrane

    PubMed Central

    Bai, Jinrong; Wu, Yanping; Liu, Xiaoyan; Zhong, Kai; Huang, Yina; Gao, Hong

    2015-01-01

    Shikimic acid (SA) has been reported to possess antibacterial activity against Staphylococcus aureus, whereas the mode of action of SA is still elusive. In this study, the antibacterial activity and mechanism of SA toward S. aureus by cell membrane damage was investigated. After SA treatment, massive K+ and nucleotide leakage from S. aureus, and a significant change in the membrane potential was observed, suggesting SA may act on the membrane by destroying the cell membrane permeability. Through transmission electron microscopic observations we further confirmed that SA can disrupt the cell membrane and membrane integrity. Meanwhile, SA was found to be capable of reducing the membrane fluidity of the S. aureus cell. Moreover, the fluorescence experiments indicated that SA could quench fluorescence of Phe residues of the membrane proteins, thus demonstrating that SA can bind to S. aureus membrane proteins. Therefore, these results showed the antibacterial activity of SA against S. aureus could be caused by the interactions of SA with S. aureus membrane proteins and lipids, resulting in causing cell membrane dysfunction and bacterial damage or even death. This study reveals the potential use of SA as an antibacterial agent. PMID:26580596

  7. Determination of short-chain fatty acids in serum by hollow fiber supported liquid membrane extraction coupled with gas chromatography.

    PubMed

    Zhao, Guohua; Liu, Jing-Fu; Nyman, Margareta; Jönsson, Jan Ake

    2007-02-01

    A method based on hollow fiber supported liquid membrane extraction coupled with a gas chromatograph equipped with flame ionization detector (GC-FID) was developed for the determination of six short-chain fatty acids including acetic acid, propionic acid, i-butyric acid, n-butyric acid, i-valeric acid and n-valeric acid in serum. Hollow fiber supported liquid membrane extraction was employed for preconcentration and clean-up of the samples. The fatty acids were extracted from the acidic donor (diluted serum) into a liquid membrane formed in the wall of the hollow fiber with 10% tri-n-octylphoshphine oxide (TOPO) in di-n-hexyl ether, and then extracted back into a basic acceptor solution filled in the lumen of the hollow fiber. After being acidified with HCl, the acceptor was directly analyzed by GC-FID. The acceptor concentration, donor pH, membrane liquid and extracting time were optimized giving an enrichment factor up to 155 times. The good linearity (r(2)>0.980), reasonable recovery (87.2-121%), and satisfactory intra-assay (8.2-11.5%) and inter-assay (6.1-11.6%) precision illustrated the good performance of the present method. Limits of detection (LOD) ranged from 0.04 to 0.24 microM and limits of quantification (LOQ) varied from 0.13 to 0.80 microM. PMID:17070116

  8. Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid.

    PubMed

    Diakogiannis, Ioannis; Berberi, Anita; Siapi, Eleni; Arkoudi-Vafea, Angeliki; Giannopoulou, Lydia; Mastronicolis, Sofia K

    2013-01-01

    This study addresses a major issue in microbial food safety, the elucidation of correlations between acid stress and changes in membrane fluidity of the pathogen Listeria monocytogenes. In order to assess the possible role that membrane fluidity changes play in L. monocytogenes tolerance to antimicrobial acids (acetic, lactic, hydrochloric acid at low pH or benzoic acid at neutral pH), the growth of the bacterium and the gel-to-liquid crystalline transition temperature point (T m) of cellular lipids of each adapted culture was measured and compared with unexposed cells. The T m of extracted lipids was measured by differential scanning calorimetry. A trend of increasing T m values but not of equal extent was observed upon acid tolerance for all samples and this increase is not directly proportional to each acid antibacterial action. The smallest increase in T m value was observed in the presence of lactic acid, which presented the highest antibacterial action. In the presence of acids with high antibacterial action such as acetic, hydrochloric acid or low antibacterial action such as benzoic acid, increased T m values were measured. The T m changes of lipids were also correlated with our previous data about fatty acid changes to acid adaptation. The results imply that the fatty acid changes are not the sole adaptation mechanism for decreased membrane fluidity (increased T m). Therefore, this study indicates the importance of conducting an in-depth structural study on how acids commonly used in food systems affect the composition of individual cellular membrane lipid molecules.

  9. Effect of chronic acetaldehyde intoxication on ethanol tolerance and membrane fatty acids.

    PubMed

    Latge, C; Lamboeuf, Y; Roumec, C; de Saint Blanquat, G

    1987-09-01

    Recent studies have suggested that acetaldehyde participates directly in the pathogenesis of alcoholism. Its action has been attributed mainly to its physico-chemical properties. Results of direct intoxication of laboratory animals with acetaldehyde have been reported, but only for short periods of exposure and at high doses. These are probably not representative of the conditions found during alcohol intoxication. The pulmonary route of administration described here enables long term intoxication with acetaldehyde, at levels corresponding to values measured during chronic ethanol intoxication. Chronic administration of acetaldehyde during 3 weeks induced a metabolic tolerance to ethanol as tested by the sleeping time after a challenge dose of ethanol; behavioural tolerance (measured by blood alcohol levels on waking) was not observed. At the end of the intoxication, phospholipid fatty acids of erythrocyte and synaptosome membranes were also analysed. Small changes in levels of the shorter fatty acids were observed in the phosphatidyl-choline fraction. By comparison with the effects of ethanol on the same membrane preparations, only a small part of this effect can be attributed to acetaldehyde. The first metabolite of ethanol has, however, a sure effect on the pattern of fatty acid phospholipids.

  10. Investigation of Enantioselective Membrane Permeability of α-Lipoic Acid in Caco-2 and MDCKII Cell.

    PubMed

    Uchida, Ryota; Okamoto, Hinako; Ikuta, Naoko; Terao, Keiji; Hirota, Takashi

    2016-01-26

    α-Lipoic acid (LA) contains a chiral carbon and exists as two enantiomers (R-α-lipoic acid (RLA) and S-α-lipoic acid (SLA)). We previously demonstrated that oral bioavailability of RLA is better than that of SLA. This difference arose from the fraction absorbed multiplied by gastrointestinal availability (F(a) × F(g)) and hepatic availability (F(h)) in the absorption phase. However, it remains unclear whether F(a) and/or F(g) are involved in enantioselectivity. In this study, Caco-2 cells and Madin-Darby canine kidney strain II cells were used to assess the enantioselectivity of membrane permeability. LA was actively transported from the apical side to basal side, regardless of the differences in its steric structure. Permeability rates were proportionally increased in the range of 10-250 µg LA/mL, and the permeability coefficient did not differ significantly between enantiomers. Hence, we conclude that enantioselective pharmacokinetics arose from the metabolism (F(h) or F(g) × F(h)), and definitely not from the membrane permeation (F(a)) in the absorption phase.

  11. Investigation of Enantioselective Membrane Permeability of α-Lipoic Acid in Caco-2 and MDCKII Cell

    PubMed Central

    Uchida, Ryota; Okamoto, Hinako; Ikuta, Naoko; Terao, Keiji; Hirota, Takashi

    2016-01-01

    α-Lipoic acid (LA) contains a chiral carbon and exists as two enantiomers (R-α-lipoic acid (RLA) and S-α-lipoic acid (SLA)). We previously demonstrated that oral bioavailability of RLA is better than that of SLA. This difference arose from the fraction absorbed multiplied by gastrointestinal availability (Fa × Fg) and hepatic availability (Fh) in the absorption phase. However, it remains unclear whether Fa and/or Fg are involved in enantioselectivity. In this study, Caco-2 cells and Madin–Darby canine kidney strain II cells were used to assess the enantioselectivity of membrane permeability. LA was actively transported from the apical side to basal side, regardless of the differences in its steric structure. Permeability rates were proportionally increased in the range of 10–250 µg LA/mL, and the permeability coefficient did not differ significantly between enantiomers. Hence, we conclude that enantioselective pharmacokinetics arose from the metabolism (Fh or Fg × Fh), and definitely not from the membrane permeation (Fa) in the absorption phase. PMID:26821014

  12. Effect of medium-chain glycerides on the membrane transport of D-glucose and sulfanilic acid in the intestinal brush-border membrane vesicles.

    PubMed

    Sagara, K; Higaki, K; Yamazaki, A; Hashida, M; Sezaki, H

    1990-01-01

    To clarify the influence of medium-chain glycerides (MCG) on a biological membrane, we investigated the membrane transport of D-glucose and sulfanilic acid in the brush-border membrane (BBM) vesicles pretreated with MCG. The size distribution of the BBM vesicles determined by electron microscopic observation was not significantly different between the vesicles incorporated with MCG and those of the control. However, the amount of D-glucose taken up by the vesicles at an equilibrated stage (30 min) was significantly decreased in the MCG-treated ones based on unit content of protein. Based on these results we estimated the membrane transport of D-glucose and sulfanilic acid in consideration of vesiculation or filter-capturing efficiency in MCG-treated vesicles. The rates of Na+ gradient-independent D-glucose transport and sulfanilic acid transport were significantly greater in MCG-treated vesicles than in the control. On the other hand, the magnitude of overshooting effect in Na+ gradient-dependent uptake of D-glucose in MCG-treated vesicles was maintained similar to the control. Comparison of kinetic parameters for active D-glucose transport at different concentrations indicated that Km and Vmax were not significantly different between MCG-treated and the control vesicles. These results indicated that passive diffusion of D-glucose and sulfanilic acid was significantly increased but Na(+)-glucose cotransporter was not significantly changed by the incorporation of MCG in the intestinal BBM vesicles.

  13. Free Fatty Acids Regulate Two Galactosyltransferases in Chloroplast Envelope Membranes Isolated from Spinach Leaves

    PubMed Central

    Sakaki, Takeshi; Kondo, Noriaki; Yamada, Mitsuhiro

    1990-01-01

    Effects of MgCl2 and free fatty acids (FFA) on galactolipid:galactolipid galactosyltransferase (GGGT) and UDP-galactose: 1,2-diacylglycerol galactosyltransferase (UDGT) in chloroplast envelope membranes isolated from spinach (Spinacia oleracea L.) leaves were examined. GGGT activity was sigmoidally stimulated by MgCl2 with a saturated concentration of more than 5 millimolar. Free α-linolenic acid (18:3) caused a drastic increase in GGGT activity under limiting concentrations of MgCl2, without affecting its maximum activity at higher MgCl2 concentrations. Free 18:3 alone did not affect the GGGT activity. The effective species of FFA for the stimulation of GGGT activity in the presence of MgCl2 were unsaturated 16- and 18-carbon fatty acids. GGGT activity was also stimulated by 18:3 in the presence of MnCl2, CaCl2 and a high concentration of KCl in place of MgCl2. UDGT activity was hyperbolically enhanced by MgCl2 with a saturated concentration of 1 to 2 millimolar. In contrast to GGGT, UDGT was severely inhibited by 18:3, and MgCl2-induced stimulation was completely abolished by 18:3. Unsaturated 16- and 18-carbon fatty acids were more inhibitory to UDGT than the saturated acids. The dependence of GGGT activity on monogalactosyldiacylglycerol (MGDG) and MgCl2 concentrations was identical in the envelope membranes isolated from non- and ozone (0.5 microliter/liter)-fumigated spinach leaves, indicating that GGGT remained active in the leaves during ozone fumigation. The results are discussed in relation to the regulation of galactolipid biosynthesis by the endogenous FFA in the envelopes and to the involvement of GGGT in the triacylglycerol synthesis from MGDG in ozone-fumigated leaves. PMID:16667779

  14. Research on the Changes to the Lipid/Polymer Membrane Used in the Acidic Bitterness Sensor Caused by Preconditioning.

    PubMed

    Harada, Yuhei; Noda, Junpei; Yatabe, Rui; Ikezaki, Hidekazu; Toko, Kiyoshi

    2016-01-01

    A taste sensor that uses lipid/polymer membranes can evaluate aftertastes felt by humans using Change in membrane Potential caused by Adsorption (CPA) measurements. The sensor membrane for evaluating bitterness, which is caused by acidic bitter substances such as iso-alpha acid contained in beer, needs an immersion process in monosodium glutamate (MSG) solution, called "MSG preconditioning". However, what happens to the lipid/polymer membrane during MSG preconditioning is not clear. Therefore, we carried out three experiments to investigate the changes in the lipid/polymer membrane caused by the MSG preconditioning, i.e., measurements of the taste sensor, measurements of the amount of the bitterness substance adsorbed onto the membrane and measurements of the contact angle of the membrane surface. The CPA values increased as the preconditioning process progressed, and became stable after 3 d of preconditioning. The response potentials to the reference solution showed the same tendency of the CPA value change during the preconditioning period. The contact angle of the lipid/polymer membrane surface decreased after 7 d of MSG preconditioning; in short, the surface of the lipid/polymer membrane became hydrophilic during MSG preconditioning. The amount of adsorbed iso-alpha acid was increased until 5 d preconditioning, and then it decreased. In this study, we revealed that the CPA values increased with the progress of MSG preconditioning in spite of the decrease of the amount of iso-alpha acid adsorbed onto the lipid/polymer membrane, and it was indicated that the CPA values increase because the sensor sensitivity was improved by the MSG preconditioning. PMID:26891299

  15. Purified membrane and soluble folate binding proteins from cultured KB cells have similar amino acid compositions and molecular weights but differ in fatty acid acylation.

    PubMed Central

    Luhrs, C A; Pitiranggon, P; da Costa, M; Rothenberg, S P; Slomiany, B L; Brink, L; Tous, G I; Stein, S

    1987-01-01

    A membrane-associated folate binding protein (FBP) and a soluble FBP, which is released into the culture medium, have been purified from human KB cells using affinity chromatography. By NaDodSO4/PAGE, both proteins have an apparent Mr of approximately 42,000. However, in the presence of Triton X-100, the soluble FBP eluted from a Sephadex G-150 column with an apparent Mr of approximately 40,000 (similar to NaDodSO4/PAGE) but the membrane-associated FBP eluted with an apparent Mr of approximately 160,000, indicating that this species contains a hydrophobic domain that interacts with the detergent micelles. The amino acid compositions of both forms of FBP were similar, especially with respect to the apolar amino acids. In addition, the 18 amino acids at the amino termini of both proteins were identical. The membrane FBP, following delipidation with chloroform/methanol, contained 7.1 mol of fatty acid per mol of protein, of which 4.7 mol was amide-linked and 2.4 mol was ester-linked. The soluble FBP contained only 0.05 mol of fatty acid per mol of protein. These studies indicate that the membrane FBP of KB cells contains covalently bound fatty acids that may serve to anchor the protein in the cell membrane. Images PMID:3476960

  16. Purified membrane and soluble folate binding proteins from cultured KB cells have similar amino acid compositions and molecular weights but differ in fatty acid acylation

    SciTech Connect

    Luhrs, C.A.; Pitiranggon, P.; Costa, M.D.; Rothenberg, S.P.; Slomiany, B.L.; Brink, L.; Tous, G.I.; Stein, S.

    1987-09-01

    A membrane-associated folate binding protein (FBP) and a soluble FBP, which is released into the culture medium, have been purified from human KB cells using affinity chromatography. By NaDodSO/sub 4/PAGE, both proteins have an apparent M/sub r/ of approx. 42,000. However, in the presence of Triton X-100, the soluble FBP eluted from a Sephadex G-150 column with an apparent M/sub r/ of approx. 40,000 (similar to NaDodSO/sub 4/PAGE) but the membrane-associated FBP eluted with an apparent M/sub r/ of approx. = 160,000, indicating that this species contains a hydrophobic domain that interacts with the detergent micelles. The amino acid compositions of both forms of FBP were similar, especially with respect to the apolar amino acids. In addition, the 18 amino acids at the amino termini of both proteins were identical. The membrane FBP, following delipidation with chloroformmethanol, contained 7.1 mol of fatty acid per mol of protein, of which 4.7 mol was amide-linked and 2.4 mol was ester-linked. The soluble FBP contained only 0.05 mol of fatty acid per mol of protein. These studies indicate that the membrane FBP of KB cells contains covalently bound fatty acids that may serve to anchor the protein in the cell membrane.

  17. Short branched-chain C6 carboxylic acids result in increased growth, novel 'unnatural' fatty acids and increased membrane fluidity in a Listeria monocytogenes branched-chain fatty acid-deficient mutant.

    PubMed

    Sen, Suranjana; Sirobhushanam, Sirisha; Hantak, Michael P; Lawrence, Peter; Brenna, J Thomas; Gatto, Craig; Wilkinson, Brian J

    2015-10-01

    Listeria monocytogenes is a psychrotolerant food borne pathogen, responsible for the high fatality disease listeriosis, and expensive food product recalls. Branched-chain fatty acids (BCFAs) of the membrane play a critical role in providing appropriate membrane fluidity and optimum membrane biophysics. The fatty acid composition of a BCFA-deficient mutant is characterized by high amounts of straight-chain fatty acids and even-numbered iso fatty acids, in contrast to the parent strain where odd-numbered anteiso fatty acids predominate. The presence of 2-methylbutyrate (C5) stimulated growth of the mutant at 37°C and restored growth at 10°C along with the content of odd-numbered anteiso fatty acids. The C6 branched-chain carboxylic acids 2-ethylbutyrate and 2-methylpentanoate also stimulated growth to a similar extent as 2-methylbutyrate. However, 3-methylpentanoate was ineffective in rescuing growth. 2-Ethylbutyrate and 2-methylpentanoate led to novel major fatty acids in the lipid profile of the membrane that were identified as 12-ethyltetradecanoic acid and 12-methylpentadecanoic acid respectively. Membrane anisotropy studies indicated that growth of strain MOR401 in the presence of these precursors increased its membrane fluidity to levels of the wild type. Cells supplemented with 2-methylpentanoate or 2-ethylbutyrate at 10°C shortened the chain length of novel fatty acids, thus showing homeoviscous adaptation. These experiments use the mutant as a tool to modulate the membrane fatty acid compositions through synthetic precursor supplementation, and show how existing enzymes in L. monocytogenes adapt to exhibit non-native activity yielding unique 'unnatural' fatty acid molecules, which nevertheless possess the correct biophysical properties for proper membrane function in the BCFA-deficient mutant.

  18. Short branched-chain C6 carboxylic acids result in increased growth, novel 'unnatural' fatty acids and increased membrane fluidity in a Listeria monocytogenes branched-chain fatty acid-deficient mutant.

    PubMed

    Sen, Suranjana; Sirobhushanam, Sirisha; Hantak, Michael P; Lawrence, Peter; Brenna, J Thomas; Gatto, Craig; Wilkinson, Brian J

    2015-10-01

    Listeria monocytogenes is a psychrotolerant food borne pathogen, responsible for the high fatality disease listeriosis, and expensive food product recalls. Branched-chain fatty acids (BCFAs) of the membrane play a critical role in providing appropriate membrane fluidity and optimum membrane biophysics. The fatty acid composition of a BCFA-deficient mutant is characterized by high amounts of straight-chain fatty acids and even-numbered iso fatty acids, in contrast to the parent strain where odd-numbered anteiso fatty acids predominate. The presence of 2-methylbutyrate (C5) stimulated growth of the mutant at 37°C and restored growth at 10°C along with the content of odd-numbered anteiso fatty acids. The C6 branched-chain carboxylic acids 2-ethylbutyrate and 2-methylpentanoate also stimulated growth to a similar extent as 2-methylbutyrate. However, 3-methylpentanoate was ineffective in rescuing growth. 2-Ethylbutyrate and 2-methylpentanoate led to novel major fatty acids in the lipid profile of the membrane that were identified as 12-ethyltetradecanoic acid and 12-methylpentadecanoic acid respectively. Membrane anisotropy studies indicated that growth of strain MOR401 in the presence of these precursors increased its membrane fluidity to levels of the wild type. Cells supplemented with 2-methylpentanoate or 2-ethylbutyrate at 10°C shortened the chain length of novel fatty acids, thus showing homeoviscous adaptation. These experiments use the mutant as a tool to modulate the membrane fatty acid compositions through synthetic precursor supplementation, and show how existing enzymes in L. monocytogenes adapt to exhibit non-native activity yielding unique 'unnatural' fatty acid molecules, which nevertheless possess the correct biophysical properties for proper membrane function in the BCFA-deficient mutant. PMID:26225744

  19. Membrane disruption by antimicrobial fatty acids releases low-molecular-weight proteins from Staphylococcus aureus.

    PubMed

    Parsons, Joshua B; Yao, Jiangwei; Frank, Matthew W; Jackson, Pamela; Rock, Charles O

    2012-10-01

    The skin represents an important barrier for pathogens and is known to produce fatty acids that are toxic toward gram-positive bacteria. A screen of fatty acids as growth inhibitors of Staphylococcus aureus revealed structure-specific antibacterial activity. Fatty acids like oleate (18:1Δ9) were nontoxic, whereas palmitoleate (16:1Δ9) was a potent growth inhibitor. Cells treated with 16:1Δ9 exhibited rapid membrane depolarization, the disruption of all major branches of macromolecular synthesis, and the release of solutes and low-molecular-weight proteins into the medium. Other cytotoxic lipids, such as glycerol ethers, sphingosine, and acyl-amines blocked growth by the same mechanisms. Nontoxic 18:1Δ9 was used for phospholipid synthesis, whereas toxic 16:1Δ9 was not and required elongation to 18:1Δ11 prior to incorporation. However, blocking fatty acid metabolism using inhibitors to prevent acyl-acyl carrier protein formation or glycerol-phosphate acyltransferase activity did not increase the toxicity of 18:1Δ9, indicating that inefficient metabolism did not play a determinant role in fatty acid toxicity. Nontoxic 18:1Δ9 was as toxic as 16:1Δ9 in a strain lacking wall teichoic acids and led to growth arrest and enhanced release of intracellular contents. Thus, wall teichoic acids contribute to the structure-specific antimicrobial effects of unsaturated fatty acids. The ability of poorly metabolized 16:1 isomers to penetrate the cell wall defenses is a weakness that has been exploited by the innate immune system to combat S. aureus.

  20. Differential mode of attack on membrane phospholipids by an acidic phospholipase A₂ (RVVA-PLA₂-I) from Daboia russelli venom.

    PubMed

    Saikia, Debashree; Bordoloi, Naba K; Chattopadhyay, Pronobesh; Choklingam, S; Ghosh, Siddhartha S; Mukherjee, Ashis K

    2012-12-01

    An acidic phospholipase A₂ (RVVA-PLA₂-I) purified from Daboia russelli venom demonstrated dose-dependent catalytic, mitochondrial and erythrocyte membrane damaging activities. RVVA-PLA₂-I was non-lethal to mice at the tested dose, however, it affected the different organs of mice particularly the liver and cardiac tissues as deduced from the enzymatic activities measured in mice serum after injection of this PLA₂ enzyme. RVVA-PLA₂-I preferentially hydrolyzed phospholipids (phosphatidylcholine) of erythrocyte membrane compared to the liver mitochondrial membrane. Interestingly, RVVA-PLA₂-I failed to hydrolyze membrane phospholipids of HT-29 (colon adenocarcinoma) cells, which contain an abundance of phosphatidylcholine in its outer membrane, within 24h of incubation. The gas-chromatographic (GC) analysis of saturated/unsaturated fatty acids' release patterns from intact mitochondrial and erythrocyte membranes after the addition of RVVA-PLA₂-I showed a distinctly different result. The results are certainly a reflection of differences in the outer membrane phospholipid composition of tested membranes owing to which they are hydrolyzed by the venom PLA₂s to a different extent. The chemical modification of essential amino acids present in the active site, neutralization study with polyvalent antivenom and heat-inactivation of RVVA-PLA₂-I suggested the correlation between catalytic and membrane damaging activities of this PLA₂ enzyme. Our study advocates that the presence of a large number of PLA₂-sensitive phospholipid domains/composition, rather than only the phosphatidylcholine (PC) content of that particular membrane may determine the extent of membrane damage by a particular venom PLA₂ enzyme.

  1. Identification of Novel Genetic Determinants of Erythrocyte Membrane Fatty Acid Composition among Greenlanders.

    PubMed

    Andersen, Mette Korre; Jørsboe, Emil; Sandholt, Camilla Helene; Grarup, Niels; Jørgensen, Marit Eika; Færgeman, Nils Joakim; Bjerregaard, Peter; Pedersen, Oluf; Moltke, Ida; Hansen, Torben; Albrechtsen, Anders

    2016-06-01

    Fatty acids (FAs) are involved in cellular processes important for normal body function, and perturbation of FA balance has been linked to metabolic disturbances, including type 2 diabetes. An individual's level of FAs is affected by diet, lifestyle, and genetic variation. We aimed to improve the understanding of the mechanisms and pathways involved in regulation of FA tissue levels, by identifying genetic loci associated with inter-individual differences in erythrocyte membrane FA levels. We assessed the levels of 22 FAs in the phospholipid fraction of erythrocyte membranes from 2,626 Greenlanders in relation to single nucleotide polymorphisms genotyped on the MetaboChip or imputed. We identified six independent association signals. Novel loci were identified on chromosomes 5 and 11 showing strongest association with oleic acid (rs76430747 in ACSL6, beta (SE): -0.386% (0.034), p = 1.8x10-28) and docosahexaenoic acid (rs6035106 in DTD1, 0.137% (0.025), p = 6.4x10-8), respectively. For a missense variant (rs80356779) in CPT1A, we identified a number of novel FA associations, the strongest with 11-eicosenoic acid (0.473% (0.035), p = 2.6x10-38), and for variants in FADS2 (rs174570), LPCAT3 (rs2110073), and CERS4 (rs11881630) we replicated known FA associations. Moreover, we observed metabolic implications of the ACSL6 (rs76430747) and CPT1A (rs80356779) variants, which both were associated with altered HbA1c (0.051% (0.013), p = 5.6x10-6 and -0.034% (0.016), p = 3.1x10-4, respectively). The latter variant was also associated with reduced insulin resistance (HOMA-IR, -0.193 (0.050), p = 3.8x10-6), as well as measures of smaller body size, including weight (-2.676 kg (0.523), p = 2.4x10-7), lean mass (-1.200 kg (0.271), p = 1.7x10-6), height (-0.966 cm (0.230), p = 2.0x10-5), and BMI (-0.638 kg/m2 (0.181), p = 2.8x10-4). In conclusion, we have identified novel genetic determinants of FA composition in phospholipids in erythrocyte membranes, and have shown examples of

  2. Identification of Novel Genetic Determinants of Erythrocyte Membrane Fatty Acid Composition among Greenlanders

    PubMed Central

    Sandholt, Camilla Helene; Grarup, Niels; Jørgensen, Marit Eika; Færgeman, Nils Joakim; Bjerregaard, Peter; Pedersen, Oluf; Moltke, Ida; Hansen, Torben; Albrechtsen, Anders

    2016-01-01

    Fatty acids (FAs) are involved in cellular processes important for normal body function, and perturbation of FA balance has been linked to metabolic disturbances, including type 2 diabetes. An individual’s level of FAs is affected by diet, lifestyle, and genetic variation. We aimed to improve the understanding of the mechanisms and pathways involved in regulation of FA tissue levels, by identifying genetic loci associated with inter-individual differences in erythrocyte membrane FA levels. We assessed the levels of 22 FAs in the phospholipid fraction of erythrocyte membranes from 2,626 Greenlanders in relation to single nucleotide polymorphisms genotyped on the MetaboChip or imputed. We identified six independent association signals. Novel loci were identified on chromosomes 5 and 11 showing strongest association with oleic acid (rs76430747 in ACSL6, beta (SE): -0.386% (0.034), p = 1.8x10-28) and docosahexaenoic acid (rs6035106 in DTD1, 0.137% (0.025), p = 6.4x10-8), respectively. For a missense variant (rs80356779) in CPT1A, we identified a number of novel FA associations, the strongest with 11-eicosenoic acid (0.473% (0.035), p = 2.6x10-38), and for variants in FADS2 (rs174570), LPCAT3 (rs2110073), and CERS4 (rs11881630) we replicated known FA associations. Moreover, we observed metabolic implications of the ACSL6 (rs76430747) and CPT1A (rs80356779) variants, which both were associated with altered HbA1c (0.051% (0.013), p = 5.6x10-6 and -0.034% (0.016), p = 3.1x10-4, respectively). The latter variant was also associated with reduced insulin resistance (HOMA-IR, -0.193 (0.050), p = 3.8x10-6), as well as measures of smaller body size, including weight (-2.676 kg (0.523), p = 2.4x10-7), lean mass (-1.200 kg (0.271), p = 1.7x10-6), height (-0.966 cm (0.230), p = 2.0x10-5), and BMI (-0.638 kg/m2 (0.181), p = 2.8x10-4). In conclusion, we have identified novel genetic determinants of FA composition in phospholipids in erythrocyte membranes, and have shown examples of

  3. Modification and improvement of proton-exchange membrane fuel cells via treatment using peracetic acid

    NASA Astrophysics Data System (ADS)

    Xu, Zhiqiang; Qi, Zhigang; Kaufman, Arthur

    Electrodes and catalyst-coated membranes (CCMs) were treated using peracetic acid. After such a treatment, the properties and performance of these electrodes and CCMs were changed in several aspects. First, their catalytic activity was increased compared to the untreated counterparts. Second, their ability to hold water within the catalyst layers was increased so that the cathode did not need to be humidified. Third, if the cathode was humidified together with the anode, some of the electrodes were more readily to be flooded than the untreated counterparts.

  4. Nitric Acid Dehydration Using Perfluoro Carboxylate and Mixed Sulfonate/Carboxylate Membranes

    SciTech Connect

    Ames, Richard L.

    2004-09-01

    Perfluoro ionomer membranes are tetrafluoro ethylene-based materials with microheterogeneous structures consisting of a hydrophobic polymer backbone and a hydrophilic side-chain cluster region. Due to the ionomer cluster morphology, these films exhibit unique transport properties. Recent investigations with perfluoro sulfonate and perfluoro sulfonate/carboxylate composite polymers have demonstrated their value in the dehydration of nitric acid and they show potential as an alternative to conventional, energy intensive unit operations in the concentration of acid feeds. As a result, investigations were conducted to determine the feasibility of using pure perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films for the dehydration of nitric acid because of the speculation of improved water selectivity of the carboxylate pendant chain. During the first phase of these investigations the effort was focused on generating a thin, solution cast perfluoro carboxylate ionomer film, to evaluate the general, chemical and physical characteristics of the polymer, and to assess the material's aqueous transport performance (flux and nitrate separation efficiencies) in pervaporation and high-pressure environments. Results demonstrated that generating robust solution-cast films was difficult yet a number of membranes survived high trans-membrane pressures up to 700 psig. General characterization of the solution cast product showed reduced ion exchange capacities when compared with thicker, ''as received'' perfluoro carboxylate and similar sulfonate films. Small angle x-ray scattering analysis results suggested that the solution cast carboxylate films contained a small fraction of sulfonate terminated side-chains. Aqueous transport experimentation showed that permeate fluxes for both pure water and nitric acid were approximately two orders of magnitude smaller for the carboxylate solution cast membranes when compared to their sulfonate counterparts of similar thickness

  5. Steric hindrance of 2,6-disubstituted benzoic acid derivatives on the uptake via monocarboxylic acid transporters from the apical membranes of Caco-2 cells.

    PubMed

    Tsukagoshi, Kensuke; Kimura, Osamu; Endo, Tetsuya

    2014-05-01

    Benzoic acid is a typical substrate for monocarboxylic acid transporters (MCTs), and easily taken up from the apical membranes of Caco-2 cells by MCTs. However, some benzoic acid derivatives were sparingly taken up by Caco-2 cells. To elucidate the mechanism of lower uptake of the derivatives, we investigated the effect of substitution of benzene ring on the uptake by MCTs using Caco-2 cells. Among the benzoic acid derivatives tested, the uptake of 2,6-disubstituted benzoic acids was markedly lower than that of other benzoic acids. Co-incubation of the 2,6-disubstituted derivatives with benzoic acid did not decrease the uptake of benzoic acid, while co-incubation with other derivatives significantly decreased the uptake of benzoic acid. Kinetic analyses elucidated that the uptake of 2,6-dichlorobenzoic acid and 2,3,6-trichlorobenzoic acid did not involve the carrier-mediated process. The 2,6-disubstitution of benzoic acid may prevent the access of carboxylic acid group to MCTs expressed on the apical membranes of Caco-2 cells. PMID:24861932

  6. Membrane potential and proton cotransport of alanine and phosphate as affected by permeant weak acids in Lemna gibba

    SciTech Connect

    Basso, B.; Ullrich-Eberius, C.I.

    1987-11-01

    The treatment of Lemna gibba plants with the weak acids (trimethylacetic acid and butyric acid), used as tools to decrease intracellular pH, induced a hyperpolarization of membrane potential, dependent on the concentration of the undissociated permeant form of the weak acid and on the value of the resting potential. Measurements were carried out both with high potential and low potential plants and the maximum values of acid induced hyperpolarization were about 35 and 71 millivolts, respectively. Weak acids influenced also the transient light-dark membrane potential changes, typical for photosynthesizing material, suggesting a dependence of these changes on an acidification of cytoplasm. In the presence of the weak acids, the membrane depolarization induced by the cotransport of alanine and phosphate with protons was reduced; the maximum reduction (about 90%) was obtained with alanine during 2 millimolar trimethylacetic acid perfusion at pH 5. A strong inhibition of the uptake rates (up to 48% for (/sup 14/C)alanine and 68% for /sup 32/P-phosphate) was obtained in the presence of the weak acids, both by decreasing the pH of the medium and by increasing the concentration of the acid. In these experimental conditions, the ATP level and O/sub 2/ uptake rates did not change significantly. These results constitute good evidence that H/sup +//solute cotransport in Lemna, already known to be dependent on the electrochemical potential difference for protons, is also strongly regulated by the cytoplasmic pH value.

  7. Acid-extrusion from tissue: the interplay between membrane transporters and pH buffers.

    PubMed

    Hulikova, Alzbeta; Harris, Adrian L; Vaughan-Jones, Richard D; Swietach, Pawel

    2012-01-01

    The acid-base balance of cells is related to the concentration of free H⁺ ions. These are highly reactive, and their intracellular concentration must be regulated to avoid detrimental effects to the cell. H⁺ ion dynamics are influenced by binding to chelator substances ('buffering'), and by the production, diffusion and membrane-transport of free H⁺ ions or of the H⁺-bound chelators. Intracellular pH (pHi) regulation aims to balance this system of diffusion-reaction-transport processes at a favourable steady-state pHi. The ability of cells to regulate pHi may set a limit to tissue growth and can be subject to selection pressures. Cancer cells have been postulated to respond favourably to such selection pressures by evolving a better means of pHi regulation. A particularly important feature of tumour pHi regulation is acid-extrusion, which involves H⁺-extrusion and HCO₃⁻-uptake by membrane-bound transporter-proteins. Extracellular CO₂/HCO₃⁻ buffer facilitates these membrane-transport processes. As a mobile pH-buffer, CO₂/HCO₃⁻ protects the extracellular space from excessive acidification that could otherwise inhibit further acid-extrusion. CO₂/HCO₃⁻ also provides substrate for HCO₃⁻-transporters. However, the inherently slow reaction kinetics of CO₂/HCO₃⁻ can be rate-limiting for acid-extrusion. To circumvent this, cells can express extracellular-facing carbonic anhydrase enzymes to accelerate the attainment of equilibrium between CO₂, HCO₃⁻ and H⁺. The acid-extrusion apparatus has been proposed as a target for anti-cancer therapy. The major targets include H⁺ pumps, Na⁺/H⁺ exchangers and carbonic anhydrases. The effectiveness of such therapy will depend on the correct identification of rate-limiting steps in pHi regulation in a specific type of cancer. PMID:22360560

  8. Cellulose nanocrystal-filled poly(acrylic acid) nanocomposite fibrous membranes.

    PubMed

    Lu, Ping; Hsieh, You-Lo

    2009-10-14

    Nanocomposite fibrous membranes have been fabricated by electrospinning cellulose nanocrystal (CNC)-loaded poly(acrylic acid) (PAA) ethanol mixtures. Incorporating CNC in PAA significantly reduced fiber diameters and improved fiber uniformity. The average diameters of the as-spun nanocomposite fibers were significantly reduced from 349 nm to 162 nm, 141 nm, 90 nm and 69 nm at 5%, 10%, 15% and 20% CNC loading (by weight of a constant 4% PAA solution), respectively. CNC was well dispersed in the fibers as isolated rods oriented along the fiber axis and as spheres in the PAA matrix. The Young modulus and stress of the PAA/CNC nanocomposite fibers were significantly improved with increasing CNC loadings by up to 35-fold and 16-fold, respectively. Heat-induced esterification between the CNC surface hydroxyls and PAA carboxyl groups produced covalent crosslinks at the CNC-PAA interfaces, rendering the nanocomposite fibrous membranes insoluble in water, more thermally stable and far more superior in tensile strength. With 20% CNC, the crosslinked nanocomposite fibrous membrane exhibited a very impressive 77-fold increase in modulus and 58-fold increase in stress.

  9. Interaction of Gramicidin S and its Aromatic Amino-Acid Analog with Phospholipid Membranes

    PubMed Central

    Jelokhani-Niaraki, Masoud; Hodges, Robert S.; Meissner, Joseph E.; Hassenstein, Una E.; Wheaton, Laura

    2008-01-01

    To investigate the mechanism of interaction of gramicidin S-like antimicrobial peptides with biological membranes, a series of five decameric cyclic cationic β-sheet-β-turn peptides with all possible combinations of aromatic D-amino acids, Cyclo(Val-Lys-Leu-D-Ar1-Pro-Val-Lys-Leu-D-Ar2-Pro) (Ar ≡ Phe, Tyr, Trp), were synthesized. Conformations of these cyclic peptides were comparable in aqueous solutions and lipid vesicles. Isothermal titration calorimetry measurements revealed entropy-driven binding of cyclic peptides to POPC and POPE/POPG lipid vesicles. Binding of peptides to both vesicle systems was endothermic—exceptions were peptides containing the Trp-Trp and Tyr-Trp pairs with exothermic binding to POPC vesicles. Application of one- and two-site binding (partitioning) models to binding isotherms of exothermic and endothermic binding processes, respectively, resulted in determination of peptide-lipid membrane binding constants (Kb). The Kb1 and Kb2 values for endothermic two-step binding processes corresponded to high and low binding affinities (Kb1 ≥ 100 Kb2). Conformational change of cyclic peptides in transferring from buffer to lipid bilayer surfaces was estimated using fluorescence resonance energy transfer between the Tyr-Trp pair in one of the peptide constructs. The cyclic peptide conformation expands upon adsorption on lipid bilayer surface and interacts more deeply with the outer monolayer causing bilayer deformation, which may lead to formation of nonspecific transient peptide-lipid porelike zones causing membrane lysis. PMID:18621820

  10. n-3 Polyunsaturated fatty acids exert immunomodulatory effects on lymphocytes by targeting plasma membrane molecular organization

    PubMed Central

    Shaikh, Saame Raza; Jolly, Christopher A.; Chapkin, Robert S.

    2011-01-01

    Fish oil, enriched in bioactive n-3 polyunsaturated fatty acids (PUFA), has therapeutic value for the treatment of inflammation-associated disorders. The effects of n-3 PUFAs are pleiotropic and complex; hence, an understanding of their cellular targets and molecular mechanisms of action remains incomplete. Here we focus on recent data indicating n-3 PUFAs exert immunosuppressive effects on the function of effector and regulatory CD4+ T cells. In addition, we also present emerging evidence that n-3 PUFAs have immunomodulatory effects on B cells. We then focus on one multifaceted mechanism of n-3 PUFAs, which is the alteration of the biophysical and biochemical organization of the plasma membrane. This mechanism is central for downstream signaling, eicosanoid production, transcriptional regulation and cytokine secretion. We highlight recent work demonstrating n-3 PUFA acyl chains in the plasma membrane target the lateral organization of membrane signaling assemblies (i.e. lipid rafts or signaling networks) and de novo phospholipid biosynthesis. We conclude by proposing new functional and mechanistic questions in this area of research that will aid in the development of fish oil as adjuvant therapy for treating unresolved chronic inflammation. PMID:22020145

  11. Continuous Decolorization of Acid Blue 62 Solution in an Enzyme Membrane Reactor.

    PubMed

    Lewańczuk, Marcin; Bryjak, Jolanta

    2015-09-01

    This paper focuses on using an enzyme membrane reactor (EMR) for the effective continuous decolorization of Acid Blue 62 (AB62). The following factors were considered for the effective use of Cerrena unicolor laccase immobilized in the EMR volume: the enzyme was stable in six successive runs in a batch reactor; no aeration was necessary; AB62 and the oxidized products were sorbed onto the membrane but were not rejected; and the enzyme was stable in the EMR system. It is obvious that any continuous process must be predictable, and thus, the objective was to verify the process model experimentally. For this reason, a proper isoenzyme kinetic equation was selected and the parameters were evaluated. The obtained kinetic parameters were used to plan processes and to verify their applicability to long-term AB62 decolorization, and a very good agreement between the calculated and the measured data was obtained. In the main designed continuous decolorization process, the conversion reached 98 % and was stable for 4 days. The membrane reactor with C. unicolor laccase appears to be very promising for AB62 decolorization.

  12. Amino-terminal basic residues of Src mediate membrane binding through electrostatic interaction with acidic phospholipids.

    PubMed Central

    Sigal, C T; Zhou, W; Buser, C A; McLaughlin, S; Resh, M D

    1994-01-01

    Membrane targeting of pp60src (Src) is mediated by its myristoylated amino terminus. We demonstrate that, in addition to myristate, six basic residues in the amino terminus are essential for high-affinity binding to the lipid bilayer via electrostatic interaction with acidic phospholipids. Specifically, c-Src was shown to bind 2500-fold more strongly to vesicles composed of the physiological ratio of 2:1 phosphatidylcholine (PC)/phosphatidylserine (PS) than to neutral PC bilayer vesicles. The apparent Kd for binding of c-Src to the PC/PS bilayer was 6 x 10(-7) M. This interaction is sufficiently strong to account for c-Src membrane targeting. Mutants of c-Src in which the amino-terminal basic residues were replaced by neutral asparagine residues exhibited binding isotherms approaching that of wild-type binding to neutral bilayers (apparent Kd of 2 x 10(-3) M). The transforming v-Src and activated c-Src (Y527F) proteins also bound more strongly to PC/PS bilayers (apparent Kd of approximately 1 x 10(-5) M) than to neutral PC bilayers. In vivo experiments with Src mutants confirmed the role of positive charge in mediating membrane binding and cellular transformation. Images PMID:7527558

  13. Recovery of water and acid from leach solutions using direct contact membrane distillation.

    PubMed

    Kesieme, Uchenna K; Milne, Nicholas; Cheng, Chu Yong; Aral, Hal; Duke, Mikel

    2014-01-01

    This paper describes for the first time the use of direct contact membrane distillation (DCMD) for acid and water recovery from a real leach solution generated by a hydrometallurgical plant. The leach solutions considered contained H2SO4 or HCl. In all tests the temperature of the feed solution was kept at 60 °C. The test work showed that fluxes were within the range of 18-33 kg/m(2)/h and 15-35 kg/m(2)/h for the H2SO4 and HCl systems, respectively. In the H2SO4 leach system, the final concentration of free acid in the sample solution increased on the concentrate side of the DCMD system from 1.04 M up to 4.60 M. The sulfate separation efficiency was over 99.9% and overall water recovery exceeded 80%. In the HCl leach system, HCl vapour passed through the membrane from the feed side to the permeate. The concentration of HCl captured in the permeate was about 1.10 M leaving behind only 0.41 M in the feed from the initial concentration of 2.13 M. In all the experiments, salt rejection was >99.9%. DCMD is clearly viable for high recovery of high quality water and concentrated H2SO4 from spent sulfuric acid leach solution where solvent extraction could then be applied to recover the sulfuric acid and metals. While HCl can be recovered for reuse using only DCMD. PMID:24569289

  14. Membrane Stresses Induced by Overproduction of Free Fatty Acids in Escherichia coli▿†

    PubMed Central

    Lennen, Rebecca M.; Kruziki, Max A.; Kumar, Kritika; Zinkel, Robert A.; Burnum, Kristin E.; Lipton, Mary S.; Hoover, Spencer W.; Ranatunga, Don R.; Wittkopp, Tyler M.; Marner, Wesley D.; Pfleger, Brian F.

    2011-01-01

    Microbially produced fatty acids are potential precursors to high-energy-density biofuels, including alkanes and alkyl ethyl esters, by either catalytic conversion of free fatty acids (FFAs) or enzymatic conversion of acyl-acyl carrier protein or acyl-coenzyme A intermediates. Metabolic engineering efforts aimed at overproducing FFAs in Escherichia coli have achieved less than 30% of the maximum theoretical yield on the supplied carbon source. In this work, the viability, morphology, transcript levels, and protein levels of a strain of E. coli that overproduces medium-chain-length FFAs was compared to an engineered control strain. By early stationary phase, an 85% reduction in viable cell counts and exacerbated loss of inner membrane integrity were observed in the FFA-overproducing strain. These effects were enhanced in strains endogenously producing FFAs compared to strains exposed to exogenously fed FFAs. Under two sets of cultivation conditions, long-chain unsaturated fatty acid content greatly increased, and the expression of genes and proteins required for unsaturated fatty acid biosynthesis were significantly decreased. Membrane stresses were further implicated by increased expression of genes and proteins of the phage shock response, the MarA/Rob/SoxS regulon, and the nuo and cyo operons of aerobic respiration. Gene deletion studies confirmed the importance of the phage shock proteins and Rob for maintaining cell viability; however, little to no change in FFA titer was observed after 24 h of cultivation. The results of this study serve as a baseline for future targeted attempts to improve FFA yields and titers in E. coli. PMID:21948837

  15. Durability aspects of polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Sethuraman, Vijay Anand

    In order for the successful adoption of proton exchange membrane (PEM) fuel cell technology, it is imperative that durability is understood, quantified and improved. A number of mechanisms are known to contribute to PEMFC membrane electrode assembly (MEA) performance degradation. In this dissertation, we show, via experiments, some of the various processes that degrade the proton exchange membrane in a PEM fuel cell; and catalyst poisoning due to hydrogen sulfide (H2S) and siloxane. The effect of humidity on the chemical stability of two types of membranes, [i.e., perfluorosulfonic acid type (PFSA, NafionRTM 112) and biphenyl sulfone hydrocarbon type, (BPSH-35)] was studied by subjecting the MEAs to open-circuit voltage (OCV) decay and potential cycling tests at elevated temperatures and low inlet gas relative humidities. The BPSH-35 membranes showed poor chemical stability in ex situ Fenton tests compared to that of NafionRTM membranes. However, under fuel cell conditions, BPSH-35 MEAs outperformed NafionRTM 112 MEAs in both the OCV decay and potential cycling tests. For both membranes, (i) at a given temperature, membrane degradation was more pronounced at lower humidities and (ii) at a given relative humidity operation, increasing the cell temperature accelerated membrane degradation. Mechanical stability of these two types of membranes was also studied using relative humidity (RH) cycling. Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane (PEM) fuel cell were estimated by studying the oxygen reduction reaction (ORR) on a rotating ring disc electrode (RRDE). Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved O2 concentration and the acidity levels in HClO4. The HClO4 acidity was correlated to ionomer water activity and hence fuel cell humidity. H 2O2 formation rates showed a linear dependence on oxygen concentration and square dependence on water

  16. Functional characterization of a fatty acid double-bond hydratase from Lactobacillus plantarum and its interaction with biosynthetic membranes.

    PubMed

    Ortega-Anaya, Joana; Hernández-Santoyo, Alejandra

    2015-12-01

    Hydrogenation of linoleic acid and other polyunsaturated fatty acids is a detoxification mechanism that is present in the Lactobacillus genus of lactic bacteria. The first stage in this multi-step process is hydration of the substrate with formation of 10-hydroxy-9-cis-octadecenoic acid due to fatty-acid hydratase activity that has been detected only in the membrane-associated cell fraction; however, its interaction with the cell membrane is unknown. To provide information in this respect we characterized the homotrimeric 64.7 kDa-native protein from Lactobacillus plantarum; afterwards, it was reconstituted in proteoliposomes and analyzed by confocal fluorescence microscopy. The results showed that hydratase is an extrinsic-membrane protein and hence, the enzymatic reaction occurs at the periphery of the cell. This location may be advantageous in the detoxifying process since the toxic linoleic acid molecule can be bound to hydratase and converted to non-toxic 10-hydroxy-9-cis-octadecenoic acid before it reaches cell membrane. Additionally, we propose that the interaction with membrane periphery occurs through electrostatic contacts. Finally, the structural model of L. plantarum hydratase was constructed based on the amino acid sequence and hence, the putative binding sites with linoleic acid were identified: site 1, located in an external hydrophobic pocket at the C-terminus of the protein and site 2, located at the core and in contact with a FAD molecule. Interestingly, it was found that the linoleic acid molecule arranges around a methionine residue in both sites (Met154 and Met81, respectively) that acts as a rigid pole, thus playing a key role in binding unsaturated fatty acids.

  17. Enhanced level of n-3 fatty acid in membrane phospholipids induces lipid peroxidation in rats fed dietary docosahexaenoic acid oil.

    PubMed

    Song, J H; Miyazawa, T

    2001-03-01

    The effect of dietary docosahexaenoic acid (DHA, 22:6n-3) oil with different lipid types on lipid peroxidation was studied in rats. Each group of male Sprague-Dawley rats was pair fed 15% (w/w) of either DHA-triglycerides (DHA-TG), DHA-ethyl esters (DHA-EE) or DHA-phospholipids (DHA-PL) for up to 3 weeks. The palm oil (supplemented with 20% soybean oil) diet without DHA was fed as the control. Dietary DHA oils lowered plasma triglyceride concentrations in rats fed DHA-TG (by 30%), DHA-EE (by 45%) and DHA-PL (by 27%), compared to control. The incorporation of dietary DHA into plasma and liver phospholipids was more pronounced in the DHA-TG and DHA-EE group than in the DHA-PL group. However, DHA oil intake negatively influenced lipid peroxidation in both plasma and liver. Phospholipid peroxidation in plasma and liver was significantly higher than control in rats fed DHA-TG or DHA-EE, but not DHA-PL. These results are consistent with increased thiobarbituric acid reactive substances (TBARS) and decreased alpha-tocopherol levels in plasma and liver. In addition, liver microsomes from rats of each group were exposed to a mixture of chelated iron (Fe(3+)/ADP) and NADPH to determine the rate of peroxidative damage. During NADPH-dependent peroxidation of microsomes, the accumulation of phospholipid hydroperoxides, as well as TBARS, were elevated and alpha-tocopherol levels were significantly exhausted in DHA-TG and DHA-EE groups. During microsomal lipid peroxidation, there was a greater loss of n-3 fatty acids (mainly DHA) than of n-6 fatty acids, including arachidonic acid (20:4n-6). These results indicate that polyunsaturation of n-3 fatty acids is the most important target for lipid peroxidation. This suggests that the ingestion of large amounts of DHA oil enhances lipid peroxidation in the target membranes where greater amounts of n-3 fatty acids are incorporated, thereby increasing the peroxidizability and possibly accelerating the atherosclerotic process.

  18. Protein-dependent Membrane Interaction of A Partially Disordered Protein Complex with Oleic Acid: Implications for Cancer Lipidomics

    PubMed Central

    Chaudhuri, Arunima; Prasanna, Xavier; Agiru, Priyanka; Chakraborty, Hirak; Rydström, Anna; Ho, James C. S.; Svanborg, Catharina; Sengupta, Durba; Chattopadhyay, Amitabha

    2016-01-01

    Bovine α-lactalbumin (BLA) forms cytotoxic complexes with oleic acid (OA) that perturbs tumor cell membranes, but molecular determinants of these membrane-interactions remain poorly understood. Here, we aim to obtain molecular insights into the interaction of BLA/BLA-OA complex with model membranes. We characterized the folding state of BLA-OA complex using tryptophan fluorescence and resolved residue-specific interactions of BLA with OA using molecular dynamics simulation. We integrated membrane-binding data using a voltage-sensitive probe and molecular dynamics (MD) to demonstrate the preferential interaction of the BLA-OA complex with negatively charged membranes. We identified amino acid residues of BLA and BLA-OA complex as determinants of these membrane interactions using MD, functionally corroborated by uptake of the corresponding α-LA peptides across tumor cell membranes. The results suggest that the α-LA component of these cytotoxic complexes confers specificity for tumor cell membranes through protein interactions that are maintained even in the lipid complex, in the presence of OA. PMID:27731329

  19. Protein-dependent Membrane Interaction of A Partially Disordered Protein Complex with Oleic Acid: Implications for Cancer Lipidomics

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Arunima; Prasanna, Xavier; Agiru, Priyanka; Chakraborty, Hirak; Rydström, Anna; Ho, James C. S.; Svanborg, Catharina; Sengupta, Durba; Chattopadhyay, Amitabha

    2016-10-01

    Bovine α-lactalbumin (BLA) forms cytotoxic complexes with oleic acid (OA) that perturbs tumor cell membranes, but molecular determinants of these membrane-interactions remain poorly understood. Here, we aim to obtain molecular insights into the interaction of BLA/BLA-OA complex with model membranes. We characterized the folding state of BLA-OA complex using tryptophan fluorescence and resolved residue-specific interactions of BLA with OA using molecular dynamics simulation. We integrated membrane-binding data using a voltage-sensitive probe and molecular dynamics (MD) to demonstrate the preferential interaction of the BLA-OA complex with negatively charged membranes. We identified amino acid residues of BLA and BLA-OA complex as determinants of these membrane interactions using MD, functionally corroborated by uptake of the corresponding α-LA peptides across tumor cell membranes. The results suggest that the α-LA component of these cytotoxic complexes confers specificity for tumor cell membranes through protein interactions that are maintained even in the lipid complex, in the presence of OA.

  20. Lysophosphatidic acid produced by hen egg white lysophospholipase D induces vascular development on extraembryonic membranes.

    PubMed

    Morishige, Junichi; Uto, Yoshihiro; Hori, Hitoshi; Satouchi, Kiyoshi; Yoshiomoto, Tanihiro; Tokumura, Akira

    2013-03-01

    Lysophosphatidic acid (lysoPtdOH), a lysophospholipid mediator, exerts diverse physiological effects, including angiogenesis, through its specific G-protein-coupled receptors. Previously, we showed that unfertilized hen egg white contains polyunsaturated fatty acid-rich lysoPtdOH and lysophospholipase D (lysoPLD). Here, we examined whether lysoPtdOH was produced by lysoPLD in the presence and absence of a hen fertilized ovum and what the physiological role of lysoPtdOH in hen egg white is. Mass spectrometry showed that fertilized hen egg white contained about 8 μM lysoPtdOH before incubation with an ovum, mainly comprised of 18:1- (12.6 %), 18:2- (37.8 %) and 20:4-molecular species (41.5 %). In an early gestation period, the lysoPtdOH was increased up to 9.6 μM, concomitant with a decrease in the level of polyunsaturated lysophosphatidylcholine (lysoPtdCho). Moreover, lysoPtdOH-degrading activities were found in egg white and the vitelline membrane, showing that these enzymes control lysoPtdOH levels in egg white. In an egg yolk angiogenesis assay, two lysoPtdOH receptor antagonists, Ki16425 and N-palmitoyl serine phosphoric acid (NASP), inhibited blood vessel formation induced by exogenously added 18:1-lysoPtdOH and its precursor lysoPtdCho on the hen yolk sac. Ki16425 and NASP also inhibited blood vessel formation in the chorioallantoic membrane (CAM). Furthermore, the relatively higher levels of LPA₁, LPA₂, LPA₄ and LPA₆ mRNA were present in the yolk sac and CAM. These results suggest that lysoPtdOH produced from lysoPtdCho by the action of lysoPLD in hen egg white is involved in the formation of blood vessel networks through several lysoPtdOH receptors on various extraembryonic membranes, including the yolk sac membrane and CAM. PMID:23381130

  1. Use of Glucose Oxidase in a Membrane Reactor for Gluconic Acid Production

    NASA Astrophysics Data System (ADS)

    Das Neves, Luiz Carlos Martins; Vitolo, Michele

    This article aims at the evaluation of the catalytic performance of glucose oxidase (GO) (EC.1.1.3.4) for the glucose/gluconic acid conversion in the ultrafiltration cell type membrane reactor (MB-CSTR). The reactor was coupled with a Millipore ultrafiltration-membrane (cutoff of 100 kDa) and operated for 24 h under agitation of 100 rpm, pH 5.5, and 30°C. The experimental conditions varied were the glucose concentration (2.5, 5.0, 10.0, 20.0, and 40.0 mM), the feeding rate (0.5, 1.0, 3.0, and 6.0/h), dissolved oxygen (8.0 and 16.0 mg/L), GO concentration (2.5, 5.0, 10.0, and 20.0 UGO/mL), and the glucose oxidase/catalase activity ratio (UGO/UCAT)(1∶0, 1∶10, 1∶20, and 1∶30). A conversion yield of 80% and specific reaction rate of 40×10-4 mmol/h·UGO were attained when the process was carried out under the following conditions: D=3.0/h, dissolved oxygen=16.0 mg/L, [G]=40 mM, and (UGO/UCAT)=1∶20. A simplified model for explaining the inhibition of GO activity by hydrogen peroxide, formed during the glucose/gluconic acid conversion, was presented.

  2. Pseudomonas putida response in membrane bioreactors under salicylic acid-induced stress conditions.

    PubMed

    Collado, Sergio; Rosas, Irene; González, Elena; Gutierrez-Lavin, Antonio; Diaz, Mario

    2014-02-28

    Starvation and changing feeding conditions are frequently characteristics of wastewater treatment plants. They are typical causes of unsteady-state operation of biological systems and provoke cellular stress. The response of a membrane bioreactor functioning under feed-induced stress conditions is studied here. In order to simplify and considerably amplify the response to stress and to obtain a reference model, a pure culture of Pseudomonas putida was selected instead of an activated sludge and a sole substrate (salicylic acid) was employed. The system degraded salicylic acid at 100-1100mg/L with a high level of efficiency, showed rapid acclimation without substrate or product inhibition phenomena and good stability in response to unsteady states caused by feed variations. Under starvation conditions, specific degradation rates of around 15mg/gh were achieved during the adaptation of the biomass to the new conditions and no biofilm formation was observed during the first days of experimentation using an initial substrate to microorganisms ratio lower than 0.1. When substrate was added to the reactor as pulses resulting in rapidly changing concentrations, P. putida growth was observed only for substrate to microorganism ratios higher than 0.6, with a maximum YX/S of 0.5g/g. Biofilm development under changing feeding conditions was fast, biomass detachment only being significant for biomass concentrations on the membrane surface that were higher than 16g/m(2).

  3. Docosahexaenoic acid supplementation during pregnancy: a potential tool to prevent membrane rupture and preterm labor.

    PubMed

    Pietrantoni, Emanuela; Del Chierico, Federica; Rigon, Giuliano; Vernocchi, Pamela; Salvatori, Guglielmo; Manco, Melania; Signore, Fabrizio; Putignani, Lorenza

    2014-05-07

    Polyunsaturated fatty acids (PUFAs) are required to maintain the fluidity, permeability and integrity of cell membranes. Maternal dietary supplementation with ω-3 PUFAs during pregnancy has beneficial effects, including increased gestational length and reduced risk of pregnancy complications. Significant amounts of ω-3 docosahexaenoic acid (DHA) are transferred from maternal to fetal blood, hence ensuring high levels of DHA in the placenta and fetal bloodstream and tissues. Fetal DHA demand increases exponentially with gestational age, especially in the third trimester, due to fetal development. According to the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), a daily intake of DHA is recommended during pregnancy. Omega-3 PUFAs are involved in several anti-inflammatory, pro-resolving and anti-oxidative pathways. Several placental disorders, such as intrauterine growth restriction, premature rupture of membranes (PROM) and preterm-PROM (pPROM), are associated with placental inflammation and oxidative stress. This pilot study reports on a preliminary evaluation of the significance of the daily DHA administration on PROM and pPROM events in healthy pregnant women. Further extensive clinical trials will be necessary to fully elucidate the correlation between DHA administration during pregnancy and PROM/pPROM occurrence, which is related in turn to gestational duration and overall fetal health.

  4. Copoly(arylene ether)s containing pendant sulfonic acid groups as proton exchange membranes

    SciTech Connect

    Dae Sik, Kim; Yu Seung, Kim; Gilles, Robertson; Guiver, Michael D

    2009-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The PAE and P AEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sPAE and sPAEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (OS) of 1.0 had high ion exchange capacities (IEC{sub v})(wet) (volume-based, wet state) of 1.77 and 2.55 meq./cm3, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5 -51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the upper left-hand corner in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based), i.e., high proton conductivity and low water uptake. Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  5. Interplay of mycolic acids, antimycobacterial compounds and pulmonary surfactant membrane: a biophysical approach to disease.

    PubMed

    Pinheiro, Marina; Giner-Casares, Juan J; Lúcio, Marlene; Caio, João M; Moiteiro, Cristina; Lima, José L F C; Reis, Salette; Camacho, Luis

    2013-02-01

    This work focuses on the interaction of mycolic acids (MAs) and two antimycobacterial compounds (Rifabutin and N'-acetyl-Rifabutin) at the pulmonary membrane level to convey a biophysical perspective of their role in disease. For this purpose, accurate biophysical techniques (Langmuir isotherms, Brewster angle microscopy, and polarization-modulation infrared reflection spectroscopy) and lipid model systems were used to mimic biomembranes: MAs mimic bacterial lipids of the Mycobacterium tuberculosis (MTb) membrane, whereas Curosurf® was used as the human pulmonary surfactant (PS) membrane model. The results obtained show that high quantities of MAs are responsible for significant changes on PS biophysical properties. At the dynamic inspiratory surface tension, high amounts of MAs decrease the order of the lipid monolayer, which appears to be a concentration dependent effect. These results suggest that the amount of MAs might play a critical role in the initial access of the bacteria to their targets. Both molecules also interact with the PS monolayer at the dynamic inspiratory surface. However, in the presence of higher amounts of MAs, both compounds improve the phospholipid packing and, therefore, the order of the lipid surfactant monolayer. In summary, this work discloses the putative protective effects of antimycobacterial compounds against the MAs induced biophysical impairment of PS lipid monolayers. These protective effects are most of the times overlooked, but can constitute an additional therapeutic value in the treatment of pulmonary tuberculosis (Tb) and may provide significant insights for the design of new and more efficient anti-Tb drugs based on their behavior as membrane ordering agents.

  6. Membrane-mediated extractive fermentation for lactic acid production from cellulosic biomass

    SciTech Connect

    Chen, Rongfu; Lee, Y.Y.

    1997-12-31

    Lactic acid production from cellulosic biomass by cellulose and Lactobacillus delbrueckii was studied in a fermenter-extractor employing a microporous hollow fiber membrane (NIHF). This bioreactor system was operated under a fed-batch mode with continuous removal of lactic acid by an in situ extraction. A tertiary amine (Alamine 336) was used as an extractant for lactic acid. The extraction capacity of Alamine 336 is greatly enhanced by addition of alcohol. Long-chain alcohols serve well for this purpose since they are less toxic to micro-organism. Addition of kerosene, a diluent, was necessary to reduce the solvent viscosity. A solvent mixture of 20% Alamine 336,40% oleyl alcohol, and 40% kerosene was found to be most effective in the extraction of lactic acid. Progressive change of pH from an initial value of 5.0 down to 4.3 has significantly improved the overall performance of the simultaneous saccharification and extractive fermentation over that of constant pH operation. The change of pH was applied to promote cell growth in the early phase, and extraction in the latter phase. 20 refs., 10 figs., 1 tab.

  7. Fatty acid-dependent globotriaosyl ceramide receptor function in detergent resistant model membranes.

    PubMed

    Mahfoud, Radhia; Manis, Adam; Lingwood, Clifford A

    2009-09-01

    Glycosphingolipid (GSL) fatty acid strictly regulates verotoxin 1 (VT1) and the HIV adhesin, gp120 binding to globotriaosyl ceramide within Gb(3)/cholesterol detergent resistant membrane (DRM) vesicle constructs and in Gb(3) water-air interface monolayers in a similar manner. VT2 bound Gb(3)/cholesterol vesicles irrespective of fatty acid composition, but VT1 bound neither C18 nor C20Gb(3)vesicles. C18/C20Gb(3) were dominant negative in mixed Gb(3) fatty acid isoform vesicles, but including C24:1Gb(3) gave maximal binding. VT1 bound C18Gb(3) vesicles after cholesterol removal, but C20Gb(3)vesicles required sphingomyelin in addition for binding. HIV-1gp120 also bound C16, C22, and C24, but neither C18 nor C20Gb(3) vesicles. C18 and C20Gb(3) were, in mixtures without C24:1Gb(3), dominant negative for gp120 vesicle binding. Gp120/VT1bound C18 and C24:1Gb(3) mixtures, although neither isoform bound alone. Monolayer surface pressure measurement showed VT1, but not VT2, bound Gb(3) at cellular DRM surface pressures, and confirmed loss of VT1 and gp120 (but not VT2) specific C18Gb(3) binding. We conclude fatty-acid mediated fluidity within simple model GSL/cholesterol DRM can selectively regulate GSL carbohydrate-ligand binding.

  8. Teichoic acids and lipids associated with the membrane of a Bacillus licheniformis mutant and the membrane lipids of the parental strain.

    PubMed Central

    Button, D; Hemmings, N L

    1976-01-01

    Bacillus licheniformis 6346 MH-1 and a phosphoglucomutase-deficient poorly lytic mutant, B. licheniformis 6346 MH-5, both contain cardiolipin, phosphatidyl ethanolamine, and phosphatidyl glycerol but are devoid of phosphoglycolipids. Gentiobiosyl diglyceride is present in the parent organism but glycolipids are absent from the mutant. Lipoteichoic acid was extracted from the whole cells of MH-5 with hot aqueous phenol and contained fatty acids, glucosamine, and 1,3-polyglycerol phosphate. The fatty acids were predominantly of the branched-chain type and were esterified to hydroxyl groups of a terminal glycerol residue. The polyglycerol phosphate chains contained, on average, 32 to 40 glycerol residues, some of which were substituted at the secondary hydroxyl group with alpha-N-acylglucosaminyl residues. Phenol extraction of the supernatant fluid that remained when walls were removed from preparations of disrupted cells of MH-5 yielded membrane teichoic acid, which consisted of substituted polyglycerol phosphate but was devoid of fatty acids. PMID:977537

  9. Acidic mist reduces foliar membrane-associated calcium and impairs stomatal responsiveness in red spruce.

    PubMed

    Borer, Catherine H; Schaberg, Paul G; DeHayes, Donald H

    2005-06-01

    Acidic deposition can leach essential pools of calcium (Ca) directly from plant foliage. Because of the central role of Ca in environmental signal transduction, disruptions of labile foliar Ca pools could impair physiological responses to a variety of environmental stimuli and stressors. We investigated the possibility that acidic mist-induced depletion of membrane-associated Ca (mCa), which is one form of labile Ca, may alter stomatal responsiveness to water stress, a process known to include Ca in signal transduction cascades. Red spruce (Picea rubens Sarg.) seedlings were exposed to either pH 3.0 or pH 5.0 mist treatments for one growing season. Foliar nutrition was assessed following treatments, and declines in stomatal conductance and net photosynthesis were measured on current-year shoots following stem excision. Seedlings exposed to pH 3.0 acidic mist treatments had reduced mCa relative to the pH 5.0 treated seedlings. Seedlings subjected to the pH 3.0 acidic mist treatment exhibited impaired stomatal functions, including a smaller maximum aperture, slower closure and an increased lag time between stomatal closure and photosynthetic decline following experimental water stress. Delayed stomatal closure could undermine desiccation avoidance mechanisms. Previous work has demonstrated that acidic mist treatments deplete mCa in red spruce and impair cold tolerance, with similar effects in other species. The results we present provide further evidence that acidic mist-induced mCa depletion may cause disruption of a broad range of plant stress responses.

  10. The impact of humic and fulvic acids on the dynamic properties of liposome membranes: the ESR method.

    PubMed

    Man, Dariusz; Pisarek, Izabella; Braczkowski, Michał; Pytel, Barbara; Olchawa, Ryszard

    2014-06-01

    This paper presents the results of research on the influence of two fractions of humic substances (HS): fulvic acids (FA) and humic acids (HA), as a function of concentration, on the liposome membranes formed from egg yolk lecithin (EYL). The concentration of HS in relation to EYL changed from 0% to 10% by weight. The influence of HS on various areas of membranes: interphase water-lipid, in the lipid layer just below the polar part of the membrane and in the middle of the lipid bilayer, was investigated by different spin labels (TEMPO, DOXYL 5, DOXYL 16). The study showed that HA slightly decreased the fluidity of the analyzed membranes on the surface layer, while FA significantly liquidated the center of the lipid bilayer. The strong effect of both fractions of HS on the concentration of free radicals as a function of time was also described.

  11. Nature of the charged headgroup determines the fusogenic potential and membrane properties of lithocholic acid phospholipids.

    PubMed

    Bhargava, Priyanshu; Singh, Manish; Sreekanth, Vedagopuram; Bajaj, Avinash

    2014-08-01

    Phospholipids play a crucial role in many cellular processes ranging from selective membrane permeability, to membrane fission and fusion, to cellular signaling. Headgroups of phospholipids determine the membrane properties and fusogenicity of these lipids with target cell membranes. We studied the fusogenic and membrane properties of phospholipids possessing unnatural charged headgroups with model membranes using laurdan based membrane hydration studies, DPH based membrane fluidity, and differential scanning calorimetry. We unravel that fusogenicity, membrane hydration, and fluidity of membranes are strongly contingent on the nature of the phospholipid charged headgroup. Our studies unraveled that introduction of bulky headgroups like dimethylamino pyridine induces maximum membrane hydration and perturbations with high fusogenicity as compared to small headgroup based phospholipids. These phospholipids also have the capability of high retention in DPPC membranes. Hydration and fluidity of these phospholipid-doped DPPC membranes are contingent on the nature of the charged headgroup. This study would help in future design of phospholipid based nanomaterials for effective drug delivery.

  12. FadD Is Required for Utilization of Endogenous Fatty Acids Released from Membrane Lipids ▿ †

    PubMed Central

    Pech-Canul, Ángel; Nogales, Joaquina; Miranda-Molina, Alfonso; Álvarez, Laura; Geiger, Otto; Soto, María José; López-Lara, Isabel M.

    2011-01-01

    FadD is an acyl coenzyme A (CoA) synthetase responsible for the activation of exogenous long-chain fatty acids (LCFA) into acyl-CoAs. Mutation of fadD in the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti promotes swarming motility and leads to defects in nodulation of alfalfa plants. In this study, we found that S. meliloti fadD mutants accumulated a mixture of free fatty acids during the stationary phase of growth. The composition of the free fatty acid pool and the results obtained after specific labeling of esterified fatty acids with a Δ5-desaturase (Δ5-Des) were in agreement with membrane phospholipids being the origin of the released fatty acids. Escherichia coli fadD mutants also accumulated free fatty acids released from membrane lipids in the stationary phase. This phenomenon did not occur in a mutant of E. coli with a deficient FadL fatty acid transporter, suggesting that the accumulation of fatty acids in fadD mutants occurs inside the cell. Our results indicate that, besides the activation of exogenous LCFA, in bacteria FadD plays a major role in the activation of endogenous fatty acids released from membrane lipids. Furthermore, expression analysis performed with S. meliloti revealed that a functional FadD is required for the upregulation of genes involved in fatty acid degradation and suggested that in the wild-type strain, the fatty acids released from membrane lipids are degraded by β-oxidation in the stationary phase of growth. PMID:21926226

  13. Plasma and erythrocyte membrane phospholipids and fatty acids in Italian general population and hemodialysis patients

    PubMed Central

    2014-01-01

    Background Dyslipidemia and abnormal phospholipid metabolism are frequent in uremic patients and increase their risk of cardiovascular disease (CVD): ω-3 polyunsaturated fatty acids (PUFAs) may reduce this risk in the general population. In this study we compared the plasma and erythrocyte cell membrane composition of PUFAs in a group of Caucasian hemodialysis (HD) patients and in a control group of healthy subjects and evaluated the erythrocyte/cell membrane fatty acid ratio as a marker of the dietary intake of phospholipids. The relationship between ω-3 and ω-6 fatty acids and the possible differences in PUFAs concentrations were also investigated. Methods and results After obtaining a fully informed consent, a total of ninety-nine HD patients and 160 non uremic control subjects from “Tor Vergata” University Hospital were enrolled into the study. None of them took antioxidant drugs or dietary supplements for at least 90 days prior to the observation. Blood samples were analysed by gas-chromatographic coupled to a mass spectrometric detector. The daily intake of total calories, proteins, lipids and carbohydrates is significantly lower in HD patients than in controls (p < 0.001). Most plasma and erythrocyte PUFA were also reduced significantly in HD patients (p < 0.001). Conclusions Our results suggest that many classes of PUFAs are lacking in HD patients, due to the removal of nutrients during the dialysis and to persistent malnutrition. A dietary treatment addressed to increase plasma ω-3 PUFAs and to optimize ω-6/ω-3 ratio may exert a protective action and reduce the risk of CVD in HD patient. PMID:24655786

  14. Fast Diffusion of Very Long Chain Saturated Fatty Acids across a Bilayer Membrane and Their Rapid Extraction by Cyclodextrins

    PubMed Central

    Pillai, Biju K.; Jasuja, Ravi; Simard, Jeffrey R.; Hamilton, James A.

    2009-01-01

    Abnormalities in the transport of saturated very long chain fatty acids (VLCFA; >C18:0) contribute to their toxic levels in peroxisomal disorders of fatty acid metabolism, such as adrenoleukodystrophy and adrenomyeloneuropathy. We previously showed that VLCFA desorb much slower than normal dietary fatty acids from both albumin and protein-free lipid bilayers. The important step of transbilayer movement (flip-flop) was not measured directly as a consequence of this very slow desorption from donors, and the extremely low aqueous solubility of VLCFA precludes addition of unbound VLCFA to lipid membranes. We have overcome these limitations using methyl-β-cyclodextrin to solubilize VLCFA for rapid delivery to “acceptor” phosphatidylcholine vesicles (small and large unilamellar) and to cells. VLCFA binding was monitored in real time with the fluorescent probe fluorescein-labeled phosphatidylethanolamine in the outer membrane leaflet, and entrapped pyranine was used to detect flip-flop across the membrane. The upper limit of the rate of flip-flop across the membrane was independent of temperature and media viscosity and was similar for model raft and non-raft membranes as well as living cells. We further showed that cyclodextrins can extract VLCFA rapidly (within seconds) from vesicles and cells, which have implications for the mechanism and potential alternative approaches to treat adrenoleukodystrophy. Because VLCFA diffuse through the lipid bilayer, proteins may not be required for their transport across the peroxisomal membrane. PMID:19801636

  15. Erythrocyte membrane docosapentaenoic acid levels are associated with islet autoimmunity: The Diabetes Autoimmunity Study in the Young

    PubMed Central

    Norris, Jill M.; Kroehl, Miranda; Fingerlin, Tasha E.; Frederiksen, Brittni N.; Seifert, Jennifer; Wong, Randall; Clare-Salzler, Michael; Rewers, Marian

    2013-01-01

    Aims/hypotheses We previously reported that lower n-3 fatty acid intake and levels in erythrocyte membranes were associated with increased risk of islet autoimmunity (IA) but not progression to type 1 diabetes in children at increased risk for diabetes. We hypothesise that specific n-3 fatty acids and genetic markers contribute synergistically to this increased risk of IA in the Diabetes Autoimmunity Study in the Young (DAISY). Methods DAISY is following 2547 children at increased risk for type 1 diabetes for the development of IA, defined as being positive for glutamic acid decarboxylase (GAD)65, IA-2 or insulin autoantibodies on two consecutive visits. Using a case-cohort design, erythrocyte membrane fatty acids and dietary intake were measured prospectively in 58 IA-positive children and 299 IA-negative children. Results Lower membrane levels of the n-3 fatty acid, docosapentaenoic acid (DPA), were predictive of IA (HR 0.23; 95% CI 0.09,0.55), while alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were not, adjusting for HLA and diabetes family history. We examined whether the effect of dietary intake of the n-3 fatty acid ALA on IA risk was modified by fatty acid elongation and desaturation genes. Adjusting for HLA, diabetes family history, ethnicity, energy intake and questionnaire type, ALA intake was significantly more protective for IA in the presence of an increasing number of minor alleles at FADS1 rs174556 (pinteraction=0.017), at FADS2 rs174570 (pinteraction=0.016) and at FADS2 rs174583 (pinteraction=0.045). Conclusions/interpretation The putative protective effect of n-3 fatty acids on IA may result from a complex interaction between intake and genetically-controlled fatty acid desaturation. PMID:24240437

  16. Advances in biotreatment of acid mine drainage and biorecovery of metals: 2. Membrane bioreactor system for sulfate reduction.

    PubMed

    Tabak, Henry H; Govind, Rakesh

    2003-12-01

    Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 degrees C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in

  17. Modeling of facilitated transport of phenylalanine by emulsion liquid membranes with di(2-ethylhexyl)phosphoric acid as a carrier

    SciTech Connect

    Liu, X.; Liu, D.

    1998-12-01

    A mathematical model is developed in this paper to simulate the facilitated transport of phenylalanine (Phe) in emulsion liquid membrane (ELM) systems with di(2-ethylhexyl)phosphoric acid as a carrier. The model takes into account the mass transfer in both the external aqueous phase and the organic membrane phase interfacial reaction as well as membrane breakage during agitation. The model is tested by comparing theoretical predications with experimental results using Phe extraction by ELM processes. It is found that the model is valid for simulating the facilitated transport of Phe with ELM under various experimental conditions.

  18. Advances in biotreatment of acid mine drainage and biorecovery of metals: 2. Membrane bioreactor system for sulfate reduction.

    PubMed

    Tabak, Henry H; Govind, Rakesh

    2003-12-01

    Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 degrees C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in

  19. The self-crosslinked ufasome of conjugated linoleic acid: investigation of morphology, bilayer membrane and stability.

    PubMed

    Fan, Ye; Fang, Yun; Ma, Lin

    2014-11-01

    Unsaturated fatty acid liposomes (Ufasomes) have attracted interests because of the ready availability of unsaturated fatty acids and the simple assembly strategy. However, the colloidal instability of the ufasomes hinders them from applying in the fields of drug delivery and food additives. In the present work, conjugated linoleic acid (CLA) with triple activities of bioactive, assembling and crosslinking was employed as a new molecular building block to construct ufasome and afterwards crosslinked ufasome. First, CLA ufasome was self-assembled from CLA molecules in response to pH variation, and the suitable CLA concentrations and pH ranges were determined by surface tension measurement and acid-base titration. Subsequently, the self-crosslinked CLA ufasome was prepared by intra-ufasomal crosslinking of conjugated double bonds in the CLA molecules. The morphologies of the self-crosslinked CLA ufasomes were imaged using transmission electron microscopy (TEM), from which the size of 20-50 nm and the bilayer thickness of 2.7±0.5 nm were detected. Most importantly, based on the comparison of the bilayer thicknesses of the different fatty acids, the molecular arrangement in the bilayer membrane of the self-crosslinked CLA ufasome is named "side-by-side" model contrary to the ordinary "tail-to-tail" model. The pH stability of the self-crosslinked CLA ufasome was examined in virtue of dynamic light scattering tests. Finally, in vitro release results of 5-fluorouracil from the self-crosslinked CLA ufasome showed that the process was slow and sustainable.

  20. Loss of amino acids into dialysate during hemodialysis using hydrophilic and nonhydrophilic polyester-polymer alloy and polyacrylonitrile membrane dialyzers.

    PubMed

    Yokomatsu, Atsuko; Fujikawa, Tetsuya; Toya, Yoshiyuki; Shino-Kakimoto, Midori; Itoh, Yoko; Mitsuhashi, Hiroshi; Tamura, Kouichi; Hirawa, Nobuhito; Yasuda, Gen; Umemura, Satoshi

    2014-08-01

    During hemodialysis, amino acid loss through the dialysate remained a significant problem and was not clear in some dialyzers; therefore, we investigated amino acid loss with hydrophilic and nonhydrophilic polyester-polymer alloy membranes and polyacrylonitrile membranes. Nine maintenance hemodialysis patients were studied to assess amino acid loss during hemodialysis with the three membranes. Total amino acid losses were 85.7 ± 27.2 mg/L, 83.3 ± 16.1 mg/L, and 72.1 ± 22.5 mg/L with the hydrophilic, nonhydrophilic polyester-polymer alloy, and polyacrylonitrile membranes, respectively. Amino acid losses were greater with the hydrophilic membrane compared with the polyacrylonitrile membrane for ornithine (2.0 ± 0.6 vs. 1.4 ± 0.4 mg/L, P = 0.025), phenylalanine (2.4 ± 0.9 vs. 1.8 ± 0.8 mg/L, P = 0.012), and tryptophan (0.6 ± 0.2 vs. 0.4 ± 0.2 mg/L, P = 0.023). Amino acid losses were greater with the nonhydrophilic membrane than with the polyacrylonitrile membrane for ornithine (2.0 ± 0.4 vs. 1.4 ± 0.4 mg/L, P = 0.017), phenylalanine (2.3 ± 0.5 vs. 1.8 ± 0.8 mg/L, P = 0.018), tryptophan (0.7 ± 0.2 vs. 0.4 ± 0.2 mg/L, P = 0.003), and cystine (3.2 ± 0.7 vs. 2.0 ± 0.7 mg/L, P = 0.005). In conclusion, greater losses of ornithine, phenylalanine, tryptophan, and cystine were observed with polyester-polymer alloy than with polyacrylonitrile membranes during hemodialysis. Constant attention should be paid to the amino acid loss profile to improve nutritional control in hemodialysis patients. PMID:24206420

  1. Effect of Selection for High Activity-Related Metabolism on Membrane Phospholipid Fatty Acid Composition in Bank Voles.

    PubMed

    Stawski, Clare; Valencak, Teresa G; Ruf, Thomas; Sadowska, Edyta T; Dheyongera, Geoffrey; Rudolf, Agata; Maiti, Uttaran; Koteja, Paweł

    2015-01-01

    Endothermy, high basal metabolic rates (BMRs), and high locomotor-related metabolism were important steps in the evolution of mammals. It has been proposed that the composition of membrane phospholipid fatty acids plays an important role in energy metabolism and exercise muscle physiology. In particular, the membrane pacemaker theory of metabolism suggests that an increase in cell membrane fatty acid unsaturation would result in an increase in BMR. We aimed to determine whether membrane phospholipid fatty acid composition of heart, liver, and gastrocnemius muscles differed between lines of bank voles selected for high swim-induced aerobic metabolism-which also evolved an increased BMR-and unselected control lines. Proportions of fatty acids significantly differed among the organs: liver was the least unsaturated, whereas the gastrocnemius muscles were most unsaturated. However, fatty acid proportions of the heart and liver did not differ significantly between selected and control lines. In gastrocnemius muscles, significant differences between selection directions were found: compared to control lines, membranes of selected voles were richer in saturated C18:0 and unsaturated C18:2n-6 and C18:3n-3, whereas the pattern was reversed for saturated C16:0 and unsaturated C20:4n-6. Neither unsaturation index nor other combined indexes of fatty acid proportions differed between lines. Thus, our results do not support the membrane pacemaker hypothesis. However, the differences between selected and control lines in gastrocnemius muscles reflect chain lengths rather than number of double bonds and are probably related to differences in locomotor activity per se rather than to differences in the basal or routine metabolic rate. PMID:26658414

  2. Effect of Selection for High Activity-Related Metabolism on Membrane Phospholipid Fatty Acid Composition in Bank Voles.

    PubMed

    Stawski, Clare; Valencak, Teresa G; Ruf, Thomas; Sadowska, Edyta T; Dheyongera, Geoffrey; Rudolf, Agata; Maiti, Uttaran; Koteja, Paweł

    2015-01-01

    Endothermy, high basal metabolic rates (BMRs), and high locomotor-related metabolism were important steps in the evolution of mammals. It has been proposed that the composition of membrane phospholipid fatty acids plays an important role in energy metabolism and exercise muscle physiology. In particular, the membrane pacemaker theory of metabolism suggests that an increase in cell membrane fatty acid unsaturation would result in an increase in BMR. We aimed to determine whether membrane phospholipid fatty acid composition of heart, liver, and gastrocnemius muscles differed between lines of bank voles selected for high swim-induced aerobic metabolism-which also evolved an increased BMR-and unselected control lines. Proportions of fatty acids significantly differed among the organs: liver was the least unsaturated, whereas the gastrocnemius muscles were most unsaturated. However, fatty acid proportions of the heart and liver did not differ significantly between selected and control lines. In gastrocnemius muscles, significant differences between selection directions were found: compared to control lines, membranes of selected voles were richer in saturated C18:0 and unsaturated C18:2n-6 and C18:3n-3, whereas the pattern was reversed for saturated C16:0 and unsaturated C20:4n-6. Neither unsaturation index nor other combined indexes of fatty acid proportions differed between lines. Thus, our results do not support the membrane pacemaker hypothesis. However, the differences between selected and control lines in gastrocnemius muscles reflect chain lengths rather than number of double bonds and are probably related to differences in locomotor activity per se rather than to differences in the basal or routine metabolic rate.

  3. Characterization of Naphthaleneacetic Acid Binding to Receptor Sites on Cellular Membranes of Maize Coleoptile Tissue 1

    PubMed Central

    Ray, Peter M.; Dohrmann, Ulrike; Hertel, Rainer

    1977-01-01

    Characteristics of and optimum conditions for saturable (“specific”) binding of [14C]naphthaleneacetic acid to sites located on membranous particles from maize (Zea mays L.) coleoptiles are described. Most, if not all, of the specific binding appears to be due to a single kinetic class of binding sites having a KD of 5 to 7 × 10−7m for naphthalene-1-acetic acid (NAA). Binding of NAA is insensitive to high monovalent salt concentrations, indicating that binding is not primarily ionic. However, specific binding is inhibited by Mg2+ or Ca2+ above 5 mm. Specific binding is improved by organic acids, especially citrate. Binding is heat-labile and is sensitive to agents that act either on proteins or on lipids. Specific binding is reversibly inactivated by reducing agents such as dithioerythritol; a reducible group, possibly a disulfide group, may be located at the binding site and required for its function. The affinity of the specific binding sites for auxins is modified by an unidentified dialyzable, heat-stable, apparently amphoteric, organic factor (“supernatant factor”) found in maize tissue. PMID:16659851

  4. Membrane bile acid receptor TGR5 predicts good prognosis in ampullary adenocarcinoma patients with hyperbilirubinemia

    PubMed Central

    Chen, Min-Chan; Chen, Yi-Ling; Wang, Tzu-Wen; Hsu, Hui-Ping; Lai, Ming-Derg

    2016-01-01

    Bile acids are potential carcinogens in gastrointestinal cancer, and interact with nuclear and membrane receptors to initiate downstream signaling. The effect of TGR5 [also known as G protein-coupled bile acid receptor 1 (GPBAR1)] on cancer progression is dependent on the tissue where it is activated. In this report, the function of TGR5 expression in cancer was studied using a bioinformatic approach. TGR5 expression in ampullary adenocarcinoma and normal duodenum was compared by western blotting, reverse transcription polymerase chain reaction, and immunohistochemistry (IHC). High GPBAR1 gene expression was found to be an indicator of worse prognosis in gastric and breast cancer patients, and an indication of better prognosis in ovarian cancer patients. The level of GPBAR1 gene expression was higher in bile-acid exposed cancer than in other types of cancer, and was increased in well-differentiated ampullary adenocarcinoma. Negative, weak or mild expression of TGR5 was correlated with younger age, higher plasma level of total/direct bilirubin, higher plasma concentration of CA-125, advanced tumor stage and advanced AJCC TNM stage. The disease-specific survival rate was highest in ampullary adenocarcinoma patients with high TGR5 expression and high total bilirubin level. In summary, TGR5 functions as a tumor-suppressor in patients with ampullary adenocarcinoma and preoperative hyperbilirubinemia. Further study of the suppressive mechanism may provide a new therapeutic option for patients with ampullary adenocarcinoma. PMID:27510297

  5. Membrane bile acid receptor TGR5 predicts good prognosis in ampullary adenocarcinoma patients with hyperbilirubinemia.

    PubMed

    Chen, Min-Chan; Chen, Yi-Ling; Wang, Tzu-Wen; Hsu, Hui-Ping; Lai, Ming-Derg

    2016-10-01

    Bile acids are potential carcinogens in gastrointestinal cancer, and interact with nuclear and membrane receptors to initiate downstream signaling. The effect of TGR5 [also known as G protein-coupled bile acid receptor 1 (GPBAR1)] on cancer progression is dependent on the tissue where it is activated. In this report, the function of TGR5 expression in cancer was studied using a bioinformatic approach. TGR5 expression in ampullary adenocarcinoma and normal duodenum was compared by western blotting, reverse transcription polymerase chain reaction, and immunohistochemistry (IHC). High GPBAR1 gene expression was found to be an indicator of worse prognosis in gastric and breast cancer patients, and an indication of better prognosis in ovarian cancer patients. The level of GPBAR1 gene expression was higher in bile‑acid exposed cancer than in other types of cancer, and was increased in well-differentiated ampullary adenocarcinoma. Negative, weak or mild expression of TGR5 was correlated with younger age, higher plasma level of total/direct bilirubin, higher plasma concentration of CA-125, advanced tumor stage and advanced AJCC TNM stage. The disease-specific survival rate was highest in ampullary adenocarcinoma patients with high TGR5 expression and high total bilirubin level. In summary, TGR5 functions as a tumor-suppressor in patients with ampullary adenocarcinoma and preoperative hyperbilirubinemia. Further study of the suppressive mechanism may provide a new therapeutic option for patients with ampullary adenocarcinoma. PMID:27510297

  6. The bile acid membrane receptor TGR5 as an emerging target in metabolism and inflammation.

    PubMed

    Pols, Thijs W H; Noriega, Lilia G; Nomura, Mitsunori; Auwerx, Johan; Schoonjans, Kristina

    2011-06-01

    Bile acids (BAs) are amphipathic molecules that facilitate the uptake of lipids, and their levels fluctuate in the intestine as well as in the blood circulation depending on food intake. Besides their role in dietary lipid absorption, bile acids function as signaling molecules capable to activate specific receptors. These BA receptors are not only important in the regulation of bile acid synthesis and their metabolism, but also regulate glucose homeostasis, lipid metabolism, and energy expenditure. These processes are important in diabetes and other facets of the metabolic syndrome, which represents a considerable increasing health burden. In addition to the function of the nuclear receptor FXRα in regulating local effects in the organs of the enterohepatic axis, increasing evidence points to a crucial role of the G-protein coupled receptor (GPCR) TGR5 in mediating systemic actions of BAs. Here we discuss the current knowledge on BA receptors, with a strong focus on the cell membrane receptor TGR5, which emerges as a valuable target for intervention in metabolic diseases. PMID:21145931

  7. Interaction of antitumor alpha-lactalbumin-oleic acid complexes with artificial and natural membranes.

    PubMed

    Zherelova, Olga M; Kataev, Anatoly A; Grishchenko, Valery M; Knyazeva, Ekaterina L; Permyakov, Sergei E; Permyakov, Eugene A

    2009-06-01

    The specific complexes of human alpha-lactalbumin (alpha-LA) with oleic acid (OA), HAMLET and LA-OA-17 (OA-complexes), possess cytotoxic activity against tumor cells but the mechanism of their cell penetration remains unclear. To explore the molecular mechanisms underlying interaction of the OA-complexes with the cell membrane, their interactions with small unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles and electroexcitable plasma membrane of internodal native and perfused cells of the green alga Chara corallina have been studied. The fractionation (Sephadex G-200) of mixtures of the OA-complexes with the vesicles shows that OA-binding increases the affinity of alpha-LA to DPPC vesicles. Calcium association decreases protein affinity to the vesicles; the effect being less pronounced for LA-OA-17. The voltage clamp technique studies show that LA-OA-17, HAMLET, and their constituents produce different modifying effects on the plasmalemmal ionic channels of the Chara corallina cells. The irreversible binding of OA-complexes to the plasmalemma is accompanied by changes in the activation-inactivation kinetics of developing integral transmembrane currents, suppression of the Ca(2+) current and Ca(2+)-activated Cl(-) current, and by increase in the nonspecific K(+) leakage currents. The latter reflects development of nonselective permeability of the plasma membrane. The HAMLET-induced effects on the plasmalemmal currents are less pronounced and potentiated by LA-OA-17. The control experiments with OA and intact alpha-LA show their qualitatively different and much less pronounced effects on the transmembrane ionic currents. Thus, the modification of alpha-LA by OA results in an increase in the protein association with the model lipid bilayer and in drastic irreversible changes in permeability of several types of the plasmalemmal ionic channels.

  8. Interaction of antitumor alpha-lactalbumin-oleic acid complexes with artificial and natural membranes.

    PubMed

    Zherelova, Olga M; Kataev, Anatoly A; Grishchenko, Valery M; Knyazeva, Ekaterina L; Permyakov, Sergei E; Permyakov, Eugene A

    2009-06-01

    The specific complexes of human alpha-lactalbumin (alpha-LA) with oleic acid (OA), HAMLET and LA-OA-17 (OA-complexes), possess cytotoxic activity against tumor cells but the mechanism of their cell penetration remains unclear. To explore the molecular mechanisms underlying interaction of the OA-complexes with the cell membrane, their interactions with small unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles and electroexcitable plasma membrane of internodal native and perfused cells of the green alga Chara corallina have been studied. The fractionation (Sephadex G-200) of mixtures of the OA-complexes with the vesicles shows that OA-binding increases the affinity of alpha-LA to DPPC vesicles. Calcium association decreases protein affinity to the vesicles; the effect being less pronounced for LA-OA-17. The voltage clamp technique studies show that LA-OA-17, HAMLET, and their constituents produce different modifying effects on the plasmalemmal ionic channels of the Chara corallina cells. The irreversible binding of OA-complexes to the plasmalemma is accompanied by changes in the activation-inactivation kinetics of developing integral transmembrane currents, suppression of the Ca(2+) current and Ca(2+)-activated Cl(-) current, and by increase in the nonspecific K(+) leakage currents. The latter reflects development of nonselective permeability of the plasma membrane. The HAMLET-induced effects on the plasmalemmal currents are less pronounced and potentiated by LA-OA-17. The control experiments with OA and intact alpha-LA show their qualitatively different and much less pronounced effects on the transmembrane ionic currents. Thus, the modification of alpha-LA by OA results in an increase in the protein association with the model lipid bilayer and in drastic irreversible changes in permeability of several types of the plasmalemmal ionic channels. PMID:19588235

  9. Interaction of gramicidin S and its aromatic amino-acid analog with phospholipid membranes.

    PubMed

    Jelokhani-Niaraki, Masoud; Hodges, Robert S; Meissner, Joseph E; Hassenstein, Una E; Wheaton, Laura

    2008-10-01

    To investigate the mechanism of interaction of gramicidin S-like antimicrobial peptides with biological membranes, a series of five decameric cyclic cationic beta-sheet-beta-turn peptides with all possible combinations of aromatic D-amino acids, Cyclo(Val-Lys-Leu-D-Ar1-Pro-Val-Lys-Leu-D-Ar2-Pro) (Ar identical with Phe, Tyr, Trp), were synthesized. Conformations of these cyclic peptides were comparable in aqueous solutions and lipid vesicles. Isothermal titration calorimetry measurements revealed entropy-driven binding of cyclic peptides to POPC and POPE/POPG lipid vesicles. Binding of peptides to both vesicle systems was endothermic-exceptions were peptides containing the Trp-Trp and Tyr-Trp pairs with exothermic binding to POPC vesicles. Application of one- and two-site binding (partitioning) models to binding isotherms of exothermic and endothermic binding processes, respectively, resulted in determination of peptide-lipid membrane binding constants (K(b)). The K(b1) and K(b2) values for endothermic two-step binding processes corresponded to high and low binding affinities (K(b1) >or= 100 K(b2)). Conformational change of cyclic peptides in transferring from buffer to lipid bilayer surfaces was estimated using fluorescence resonance energy transfer between the Tyr-Trp pair in one of the peptide constructs. The cyclic peptide conformation expands upon adsorption on lipid bilayer surface and interacts more deeply with the outer monolayer causing bilayer deformation, which may lead to formation of nonspecific transient peptide-lipid porelike zones causing membrane lysis.

  10. Quantitation of lysolipids, fatty acids, and phospholipase A2 activity and correlation with membrane polarity

    PubMed Central

    Singh, Jasmeet; Ranganathan, Radha

    2012-01-01

    Acrylodan-labeled rat-intestinal fatty acid binding protein, ADIFAB, binds both of lysophosphatidylcholines (LPC) and FA. Binding displaces Acrylodan and its fluorescence peak shifts from 432 to 505 nm. A fluorescence assay that relies on this shift is presented for quantitating LPC, FA, and phospholipase A2 (PLA2) activity in phospholipid bilayers in absolute units of μM/min/mg of enzyme. This is a development over an earlier assay that took into account only FA binding. Activities of bee venom PLA2 on dipalmitoylphosphatidylcholine (DPPC) and dioleylphosphatidylcholine (DOPC) bilayers were measured. Standard pH-Stat assays validated the present assay. Products increase linearly with time for about one minute in DOPC and five minutes in DPPC corresponding to completion of 5 to 8% hydrolysis in DOPC and 20% in DPPC. Membrane polarity and microviscosity measured using electron spin resonance (ESR) exhibited discontinuities at compositions that mimicked similar percentages of hydrolysis products in the respective bilayers. The observed hydrolysis rate decrease following the initial linear period thus correlates to changes in membrane polarity. The ability of the assay to yield actual product concentrations, reveal structure in the reaction progress curves, and interpretation in light of the ESR data bring insight into the shape of the reaction curve. PMID:22773689

  11. Extraction of phenol using sulfuric acid salts of trioctylamine in a supported liquid membrane

    SciTech Connect

    Wang, M.L.; Hu, K.H. )

    1994-04-01

    The extraction of phenol by trioctylamine sulfate salts in a supported-liquid membrane (SLM) process was investigated. In the extraction process, a transport model, which included the film diffusion of phenol in the aqueous phase, the membrane diffusion within the SLM, and the interfacial chemical reaction, was built. The experimental parameters, such as the cell constant ([beta]), the diffusivity of (TOA)[sub 2]H[sub 2]SO[sub 4][center dot]PhOH in the SLM (D[sub c,b]), and the mass-transfer coefficient of phenol in the aqueous solution (K[sub L]), were determined from experiments. On the basis of the experimental data and the results obtained from the transport model, the rate-controlling step of the extraction of phenol by an SLM during permeation is discussed. The effects of the operating variables and parameters, such as the initial concentration of phenol in the aqueous phase, sulfuric acid, sodium hydroxide, and trioctylamine sulfate salts, on the extraction of phenol were examined.

  12. Effects of amino acids on membrane potential and 86Rb+ fluxes in pancreatic beta-cells

    SciTech Connect

    Henquin, J.C.; Meissner, H.P.

    1981-03-01

    The membrane potential of beta-cells was studied with microelectrodes in mouse islets and their potassium permeability was evaluated by measuring 86Rb+ fluxes in rat islets. In the absence of glucose, L-leucine, its metabolite ketoisocaproate, and its nonmetabolized analogue 2-aminonorbornane-2-carboxylic acid (BCH) depolarized beta-cells and triggered bursts of electrical activity like glucose. The effect of leucine was weak, but was potentiated by a low concentration of glucose or by theophylline; the effect of ketoisocaproate was stronger and faster than that of an equimolar concentration of glucose. Arginine alone produced only a fast depolarization of beta-cells, insufficient to trigger electrical activity. Leucine and arginine potentiated the activity induced by glucose. In a glucose-free medium, alanine only slightly depolarized beta cells, whereas isoleucine and phenylalanie had no effect. Leucine, ketoisocaproate, and BCH reversibly decreased 86Rb+ efflux from islets perifused in the absence of glucose and increased 86Rb+ uptake. By contrast, both in the absence or presence of glucose, arginine increased 86Rb+ efflux and decreased 86Rb+ uptake. It is proposed that leucine, ketoisocaproate, and BCH, as glucose, deplolarize beta-cells by decreasing their potassium permeability, whereas arginine acts differently. The appearance of bursts of electrical activity with secretagogues unrelated to glucose suggests that they reflect an intrinsic property of the beta-cell membrane.

  13. Development of a Supported Emulsion Liquid Membrane System for Propionic Acid Separation in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Li, Jin; Hu, Shih-Yao B.; Wiencek, John M.

    2001-01-01

    Perstractive fermentation is a good way to increase the productivity of bioreactors. Using Propionibacteria as the model system, the feasibility of using supported emulsion liquid membrane (SELM) for perstractive fermentation is assessed in this study. Five industrial solvents were considered as the solvent for preparing the SELM. The more polar a solvent is, the higher the partition coefficient. However, toxicity of a solvent also increases with its polarity. CO-1055 (industrial decanol/octanol blend) has the highest partition coefficient toward propionic acid among the solvents that has no molecular toxicity toward Propionibacteria. A preliminary extraction study was conducted using tetradecane as solvent in a hydrophobic hollow fiber contactor. The result confirmed that SELM eliminates the equilibrium limitation of conventional liquid-liquid extraction, and allows the use of a non-toxic solvent with low partition coefficient.

  14. Tannic-Acid-Coated Polypropylene Membrane as a Separator for Lithium-Ion Batteries.

    PubMed

    Pan, Lei; Wang, Haibin; Wu, Chaolumen; Liao, Chenbo; Li, Lei

    2015-07-29

    To solve the wetting capability issue of commercial polypropylene (PP) separators in lithium-ion batteries (LIBs), we developed a simple dipping surface-coating process based on tannic acid (TA), a natural plant polyphenol. Fourier transform infrared and X-ray photoelectron measurements indicate that the TA is coated successfully on the PP separators. Scanning electron microscopy images show that the TA coating does not destroy the microporous structure of the separators. After being coated with TA, the PP separators become more hydrophilic, which not only enhances the liquid electrolyte retention ability but also increases the ionic conductivity. The battery performance, especially for power capability, is improved after being coated with TA. It indicates that this TA-coating method provides a promising process by which to develop an advanced polymer membrane separator for lithium-ion batteries.

  15. Use of glucose oxidase in a membrane reactor for gluconic acid production.

    PubMed

    das Neves, Luiz Carlos Martins; Vitolo, Michele

    2007-04-01

    This article aims at the evaluation of the catalytic performance of glucose oxidase (GO) (EC.1.1.3.4) for the glucose/gluconic acid conversion in the ultrafiltration cell type membrane reactor (MB-CSTR). The reactor was coupled with a Millipore ultrafiltration-membrane (cutoff of 100 kDa) and operated for 24 h under agitation of 100 rpm, pH 5.5, and 30 degrees C. The experimental conditions varied were the glucose concentration (2.5, 5.0, 10.0, 20.0, and 40.0 mM), the feeding rate (0.5, 1.0, 3.0, and 6.0/h), dissolved oxygen (8.0 and 16.0 mg/L), GO concentration (2.5, 5.0, 10.0, and 20.0 U(GO)/mL), and the glucose oxidase/catalase activity ratio (U(GO)/U(CAT))(1:0, 1:10, 1:20, and 1:30). A conversion yield of 80% and specific reaction rate of 40 x 10(-4) mmol/h x U(GO) were attained when the process was carried out under the following conditions: D =3.0/h, dissolved oxygen =16.0 mg/L, [G] =40 mM, and (U(GO)/U(CAT)) =1:20. A simplified model for explaining the inhibition of GO activity by hydrogen peroxide, formed during the glucose/gluconic acid conversion, was presented.

  16. Free fatty acids chain length distribution affects the permeability of skin lipid model membranes.

    PubMed

    Uchiyama, Masayuki; Oguri, Masashi; Mojumdar, Enamul H; Gooris, Gert S; Bouwstra, Joke A

    2016-09-01

    The lipid matrix in the stratum corneum (SC) plays an important role in the barrier function of the skin. The main lipid classes in this lipid matrix are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). The aim of this study was to determine whether a variation in CER subclass composition and chain length distribution of FFAs affect the permeability of this matrix. To examine this, we make use of lipid model membranes, referred to as stratum corneum substitute (SCS). We prepared SCS containing i) single CER subclass with either a single FFA or a mixture of FFAs and CHOL, or ii) a mixture of various CER subclasses with either a single FFA or a mixture of FFAs and CHOL. In vitro permeation studies were performed using ethyl-p-aminobenzoic acid (E-PABA) as a model drug. The flux of E-PABA across the SCS containing the mixture of FFAs was higher than that across the SCS containing a single FA with a chain length of 24 C atoms (FA C24), while the E-PABA flux was not effected by the CER composition. To select the underlying factors for the changes in permeability, the SCSs were examined by Fourier transform infrared spectroscopy (FTIR) and Small angle X-ray scattering (SAXS). All lipid models demonstrated a similar phase behavior. However, when focusing on the conformational ordering of the individual FFA chains, the shorter chain FFA (with a chain length of 16, 18 or 20 C atoms forming only 11m/m% of the total FFA level) had a higher conformational disordering, while the conformational ordering of the chains of the CER and FA C24 and FA C22 hardly did not change irrespective of the composition of the SCS. In conclusion, the conformational mobility of the short chain FFAs present only at low levels in the model SC lipid membranes has a great impact on the permeability of E-PABA. PMID:27287726

  17. Acetylsalicylic acid (aspirin) and salicylic acid interaction with the human erythrocyte membrane bilayer induce in vitro changes in the morphology of erythrocytes.

    PubMed

    Suwalsky, Mario; Belmar, Jessica; Villena, Fernando; Gallardo, María José; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2013-11-01

    Despite the well-documented information, there are insufficient reports concerning the effects of salicylate compounds on the structure and functions of cell membranes, particularly those of human erythrocytes. With the aim to better understand the molecular mechanisms of the interaction of acetylsalicylic acid (ASA) and salicylic acid (SA) with cell membranes, human erythrocyte membranes and molecular models were utilized. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ASA and SA to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction while DMPC unilamellar vesicles (LUV) were studied by fluorescence spectroscopy. Moreover, we took advantage of the capability of differential scanning calorimetry (DSC) to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from ASA and SA interaction with PC and PE molecules. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy, while isolated unsealed human erythrocyte membranes (IUM) were studied by fluorescence spectroscopy. Results indicated that both salicylates interact with human erythrocytes and their molecular models in a concentration-dependent manner perturbing their bilayer structures. PMID:24055635

  18. Acetylsalicylic acid (aspirin) and salicylic acid interaction with the human erythrocyte membrane bilayer induce in vitro changes in the morphology of erythrocytes.

    PubMed

    Suwalsky, Mario; Belmar, Jessica; Villena, Fernando; Gallardo, María José; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2013-11-01

    Despite the well-documented information, there are insufficient reports concerning the effects of salicylate compounds on the structure and functions of cell membranes, particularly those of human erythrocytes. With the aim to better understand the molecular mechanisms of the interaction of acetylsalicylic acid (ASA) and salicylic acid (SA) with cell membranes, human erythrocyte membranes and molecular models were utilized. These consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of ASA and SA to perturb the multibilayer structures of DMPC and DMPE was evaluated by X-ray diffraction while DMPC unilamellar vesicles (LUV) were studied by fluorescence spectroscopy. Moreover, we took advantage of the capability of differential scanning calorimetry (DSC) to detect the changes in the thermotropic phase behavior of lipid bilayers resulting from ASA and SA interaction with PC and PE molecules. In an attempt to further elucidate their effects on cell membranes, the present work also examined their influence on the morphology of intact human erythrocytes by means of defocusing and scanning electron microscopy, while isolated unsealed human erythrocyte membranes (IUM) were studied by fluorescence spectroscopy. Results indicated that both salicylates interact with human erythrocytes and their molecular models in a concentration-dependent manner perturbing their bilayer structures.

  19. Acid/base equilibria in clusters and their role in proton exchange membranes: Computational insight

    SciTech Connect

    Glezakou, Vanda A; Dupuis, Michel; Mundy, Christopher J

    2007-10-24

    We describe molecular orbital theory and ab initio molecular dynamics studies of acid/base equilibria of clusters AH:(H2O)n↔A-:H+(H2O)n in low hydration regime (n = 1-4), where AH is a model of perfluorinated sulfonic acids, RSO3H (R = CF3CF2), encountered in polymeric electrolyte membranes of fuel cells. Free energy calculations on the neutral and ion pair structures for n = 3 indicate that the two configurations are close in energy and are accessible in the fluctuation dynamics of proton transport. For n = 1,2 the only relevant configuration is the neutral form. This was verified through ab initio metadynamics simulations. These findings suggest that bases are directly involved in the proton transport at low hydration levels. In addition, the gas phase proton affinity of the model sulfonic acid RSO3H was found to be comparable to the proton affinity of water. Thus, protonated acids can also play a role in proton transport under low hydration conditions and under high concentration of protons. This work was supported by the Division of Chemical Science, Office of Basic Energy Sciences, US Department of Energy (DOE under Contract DE-AC05-76RL)1830. Computations were performed on computers of the Molecular Interactions and Transformations (MI&T) group and MSCF facility of EMSL, sponsored by US DOE and OBER located at PNNL. This work was benefited from resource of the National Energy Research Scientific Computing Centre, supported by the Office of Science of the US DOE, under Contract No. DE-AC03-76SF00098.

  20. Bipolar membrane electrodialysis for generation of hydrochloric acid and ammonia from simulated ammonium chloride wastewater.

    PubMed

    Li, Ya; Shi, Shaoyuan; Cao, Hongbin; Wu, Xinmin; Zhao, Zhijuan; Wang, Liying

    2016-02-01

    Simulated ammonium chloride wastewater was treated by a lab-scale bipolar membrane electrodialysis for the generation of HCl and NH3·H2O and desalination. The influence of initial concentration of NH4Cl, current density, salt solution volume, initial concentration of acid and base and membrane stack structure on the yields of HCl and NH3·H2O was investigated. The current efficiency and energy consumption were also examined under different conditions. The results showed that, at the current density of 48 mA/cm(2), the highest concentration of HCl and NH3·H2O with initial concentration of 110 g/L NH4Cl was 57.67 g/L and 45.85 g/L, respectively. Higher initial concentration of NH4Cl was favor to reduce unit energy consumption and increase current efficiency of the BMED system. The membrane stack voltage of BMED increased quickly under constant current when the concentration of NH4Cl contained in the solution of salt compartment was depleted below the "inflection point concentration" about 8000 mg/L. It means that the concentration of NH4Cl below 8000 mg/L was no longer suitable for BMED because of higher energy consumption. The HCl and NH3·H2O concentration increased more quickly following the increase of current density. When increasing the volume of NH4Cl, the concentration of HCl and NH3·H2O also increased. The high initial concentration of acid and base could improve the final concentration of them, while the growth rate was decreased. Compared with the BMED system with three compartments, the growth rate of HCl concentration with the two compartments was higher and its unit energy consumption was lower. It meant that the performance of the BMED system could be improved by optimizing operation conditions. The application feasibility of the generation of HCl and NH3·H2O and desalination of ammonium chloride wastewater by BMED was proved. PMID:26674548

  1. Bipolar membrane electrodialysis for generation of hydrochloric acid and ammonia from simulated ammonium chloride wastewater.

    PubMed

    Li, Ya; Shi, Shaoyuan; Cao, Hongbin; Wu, Xinmin; Zhao, Zhijuan; Wang, Liying

    2016-02-01

    Simulated ammonium chloride wastewater was treated by a lab-scale bipolar membrane electrodialysis for the generation of HCl and NH3·H2O and desalination. The influence of initial concentration of NH4Cl, current density, salt solution volume, initial concentration of acid and base and membrane stack structure on the yields of HCl and NH3·H2O was investigated. The current efficiency and energy consumption were also examined under different conditions. The results showed that, at the current density of 48 mA/cm(2), the highest concentration of HCl and NH3·H2O with initial concentration of 110 g/L NH4Cl was 57.67 g/L and 45.85 g/L, respectively. Higher initial concentration of NH4Cl was favor to reduce unit energy consumption and increase current efficiency of the BMED system. The membrane stack voltage of BMED increased quickly under constant current when the concentration of NH4Cl contained in the solution of salt compartment was depleted below the "inflection point concentration" about 8000 mg/L. It means that the concentration of NH4Cl below 8000 mg/L was no longer suitable for BMED because of higher energy consumption. The HCl and NH3·H2O concentration increased more quickly following the increase of current density. When increasing the volume of NH4Cl, the concentration of HCl and NH3·H2O also increased. The high initial concentration of acid and base could improve the final concentration of them, while the growth rate was decreased. Compared with the BMED system with three compartments, the growth rate of HCl concentration with the two compartments was higher and its unit energy consumption was lower. It meant that the performance of the BMED system could be improved by optimizing operation conditions. The application feasibility of the generation of HCl and NH3·H2O and desalination of ammonium chloride wastewater by BMED was proved.

  2. Adaptive modification of membrane phospholipid fatty acid composition and metabolic thermosuppression of brown adipose tissue in heat-acclimated rats

    NASA Astrophysics Data System (ADS)

    Saha, S. K.; Ohno, T.; Tsuchiya, K.; Kuroshima, A.

    Thermogenesis, especially facultative thermogenesis by brown adipose tissue (BAT), is less important in high ambient temperature and the heat-acclimated animals show a lower metabolic rate. Adaptive changes in the metabolic activity of BAT are generally found to be associated with a modification of membrane phospholipid fatty acid composition. However, the effect of heat acclimation on membrane phospholipid fatty acid composition is as yet unknown. In this study, we examined the thermogenic activity and phospholipid fatty acid composition of interscapular BAT from heat-acclimated rats (control: 25+/-1°C, 50% relative humidity and heat acclimation: 32+/-0.5°C, 50% relative humidity). Basal thermogenesis and the total thermogenic capacity after noradrenaline stimulation, as estimated by in vitro oxygen consumption of BAT (measured polarographically using about 1-mm3 tissue blocks), were smaller in the heat-acclimated group than in the control group. There was no difference in the tissue content of phospholipids between the groups when expressed per microgram of DNA. The phospholipid fatty acid composition was analyzed by a capillary gas chromatograph. The state of phospholipid unsaturation, as estimated by the number of double bonds per fatty acid molecule, was similar between the groups. The saturated fatty acid level was higher in the heat-acclimated group. Among the unsaturated fatty acids, heat acclimation decreased docosahexaenoic acid and oleic acid levels, and increased the arachidonic acid level. The tissue level of docosahexaenoic acid correlated with the basal oxygen consumption of BAT (r=0.6, P<0.01) and noradrenaline-stimulated maximum values of oxygen consumption (r=0.5, P<0.05). Our results show that heat acclimation modifies the BAT phospholipid fatty acids, especially the n-3 polyunsaturated fatty acid docosahexaenoic acid, which is possibly involved in the metabolic thermosuppression.

  3. Temperature-Dependent Electron Paramagnetic Resonance Studies of Docosahexaenoic Acid and Gamma Linolenic Acid Effects on Phospholipid Membranes With and Without Cholesterol

    NASA Astrophysics Data System (ADS)

    Yonar, D.; Horasanb, N.; Sünnetçioğlu, M. Maral

    2016-07-01

    Free docosahexaenoic acid (DHAn-3) and gamma linolenic acid (GLAn-6) effects on dimyristoyl phosphatidylcholine (DMPC) membranes were studied as a function of temperature by electron paramagnetic resonance (EPR) spectroscopy. 5- and 16-doxyl stearic acid (5-, 16-DS) spin labels were utilized to obtain information from the interfacial and alkyl chain region, respectively. In the studied temperature range, the presence of DHAn-3 or GLAn-6 caused decreases in maximum hyperfi ne splitting values and correlation times of DMPC membranes. Both in the interfacial region and depths of membrane, changes were more pronounced for DHAn-3 in pure DMPC. In the presence of cholesterol (CH), DHAn-3 and GLAn-6 effects were similar and more pronounced in the depths of the membrane. The changes in the structure and dynamics of samples were obtained from simulations of spectra, which indicated some changes in the number of spectral components by incorporation of DHAn-3 and GLAn-6. In the interfacial region and below the main phase transition temperature of DMPC, there was an increase in heterogeneity. For temperatures above the phase transition, a more homogeneous environment for spin label was obtained in the presence of fatty acids.

  4. Classifying Membrane Proteins in the Proteome by Using Artificial Neural Networks Based on the Preferential Parameters of Amino Acids

    NASA Astrophysics Data System (ADS)

    Bose, Subrata K.; Browne, Antony; Kazemian, Hassan; White, Kenneth

    Membrane proteins (MPs) are large set of biological macromolecules that play a fundamental role in physiology and pathophysiology for survival. From a pharma-economical perspective, though it is the fact that MPs constitute ˜75% of possible targets for novel drugs but MPs are one of the most understudied groups of proteins in biochemical research. This is mainly because of the technical difficulties of obtaining structural information about trans-membrane regions (these are small sequences that crossways the bilayer lipid membrane). It is quite useful to predict the location of transmembrane segments down the sequence, since these are the elementary structural building blocks defining their topology. There have been several attempts over the last 20 years to develop tools for predicting membrane-spanning regions but current tools are far away from achieving a considerable reliability in prediction. This study aims to exploit the knowledge and current understanding in the field of artificial neural networks (ANNs) in particular data representation through the development of a system to identify and predict membrane-spanning regions by analysing primary amino acids sequence. In this paper we present a novel neural network (NNs) architecture and algorithms for predicting membrane spanning regions from primary amino acids sequences by using their preference parameters.

  5. Nanostructured bacterial cellulose-poly(4-styrene sulfonic acid) composite membranes with high storage modulus and protonic conductivity.

    PubMed

    Gadim, Tiago D O; Figueiredo, Andrea G P R; Rosero-Navarro, Nataly C; Vilela, Carla; Gamelas, José A F; Barros-Timmons, Ana; Neto, Carlos Pascoal; Silvestre, Armando J D; Freire, Carmen S R; Figueiredo, Filipe M L

    2014-05-28

    The present study reports the development of a new generation of bio-based nanocomposite proton exchange membranes based on bacterial cellulose (BC) and poly(4-styrene sulfonic acid) (PSSA), produced by in situ free radical polymerization of sodium 4-styrenesulfonate using poly(ethylene glycol) diacrylate (PEGDA) as cross-linker, followed by conversion of the ensuing polymer into the acidic form. The BC nanofibrilar network endows the composite membranes with excellent mechanical properties at least up to 140 °C, a temperature where either pure PSSA or Nafion are soft, as shown by dynamic mechanical analysis. The large concentration of sulfonic acid groups in PSSA is responsible for the high ionic exchange capacity of the composite membranes, reaching 2.25 mmol g(-1) for a composite with 83 wt % PSSA/PEGDA. The through-plane protonic conductivity of the best membrane is in excess of 0.1 S cm(-1) at 94 °C and 98% relative humidity (RH), decreasing to 0.042 S cm(-1) at 60% RH. These values are comparable or even higher than those of ionomers such as Nafion or polyelectrolytes such as PSSA. This combination of electric and viscoelastic properties with low cost underlines the potential of these nanocomposites as a bio-based alternative to other polymer membranes for application in fuel cells, redox flow batteries, or other devices requiring functional proton conducting elements, such as sensors and actuators.

  6. [Study of photocatalytic performance of TiO2 membrane for oleic acid by FTIR-ATR technique].

    PubMed

    Lin, Hua-xiang; Wang, Xu-xu; Dai, Wen-xin; Fu, Xian-zhi

    2005-07-01

    The TiO2 membranes were prepared on glass, ceramic tile and aluminum pieces by Sol-Gel and PVD methods. A fast and exact evaluation on the photocatalytic self-cleaning performance of the membrane materials was achieved by FTIR-ATR technique using oleic acid which was laid on the surface of the membrane. The hydrophilic property of the samples was also determined by the contact angle with water. The results showed that both the TiO2 membrane prepared on glass by the Sol-Gel and PVD methods displayed good photo-induced hydrophilic property and degradation activity of oleic acid, and no difference in hydrophilic property, but the former was a little superior to the latter in photocatalytic activity. The photocatalytic conversion of oleic acid on the TiO2/glass, TiO2/ceramic tile and TiO2 aluminum piece were 92%, 85% and 46%, respectively after illumination 3.5 h, showing a distinct effect of support material property on TiO2 photocatalytic performance. The results suggested that the photocatalytic activity of TiO2 membrane coated on insulator support was higher than that coated on conductor support.

  7. N-chloroamino acids cause oxidative protein modifications in the erythrocyte membrane.

    PubMed

    Robaszkiewicz, Agnieszka; Bartosz, Grzegorz; Soszyński, Mirosław

    2008-10-01

    The increase in the amount of oxidatively modified proteins is a hallmark of ageing and age-related disorders. This paper is aimed at a verification of the hypothesis that N-chloroamino acids, products of reaction between hypochlorite generated in vivo under pathological conditions and free amino acids, may induce oxidative modifications of erythrocyte membrane proteins. The effects of N-chloroalanine, N-chloroaspartate, N-chloroserine, N-chlorolysine and N-chlorophenylalanine were compared with that of HOCl/OCl(-). All the chlorocompounds studied (except for AspCl) induced the loss of tryptophan and formylkynurenine formation accompanied by decrease of acetylcholinesterase activity and V(max) of the enzyme, without change of K(m). Only HOCl/OCl(-) induced dityrosine formation being also the most effective in the induction of carbonyl groups formation. Protein thiol oxidation studied was observed for all chlorocompounds studied but with different efficiency. The destruction of amine groups content was evident for AlaCl, LysCl and SerCl. The formation of protein aggregates was observed, due mainly but not exclusively to the formation of disulphide bonds. PMID:18586303

  8. Effect of Macerase, Oxalic Acid, and EGTA on Deep Supercooling and Pit Membrane Structure of Xylem Parenchyma of Peach.

    PubMed

    Wisniewski, M; Davis, G; Arora, R

    1991-08-01

    The object of this study was to determine if calcium cross-linking of pectin in the pit membrane of xylem parenchyma restricts water movement which results in deep supercooling. Current year shoots of ;Loring' peach (Prunus persica) were infiltrated with oxalic acid or EGTA solutions for 24 or 48 hours and then either prepared for ultrastructural analysis or subjected to differential thermal analysis. The effect of 0.25 to 1.0% pectinase (weight/volume) on deep supercooling was also investigated. The use of 5 to 50 millimolar oxalic acid and pectinase resulted in a significant reduction (flattening) of the low temperature exotherm and a distinct swelling and partial degradation of the pit membrane. EGTA (10 millimolar) for 24 or 48 hours shifted the low temperature exotherm to warmer temperatures and effected the outermost layer of the pit membrane. A hypothesis is presented on pectin-mediated regulation of deep supercooling of xylem parenchyma.

  9. Plasma membrane fatty acid-binding protein and mitochondrial glutamic-oxaloacetic transaminase of rat liver are related

    SciTech Connect

    Berk, P.D.; Potter, B.J.; Sorrentino, D.; Zhou, S.L.; Isola, L.M.; Stump, D.; Kiang, C.L.; Thung, S. ); Wada, H.; Horio, Y. )

    1990-05-01

    The hepatic plasma membrane fatty acid-binding protein (h-FABP{sub PM}) and the mitochondrial isoenzyme of glutamic-oxaloacetic transaminase (mGOT) of rat liver have similar amino acid compositions and identical amino acid sequences for residues 3-24. Both proteins migrate with an apparent molecular mass of 43 kDa on SDS/polyacrylamide gel electrophoresis, have a similar pattern of basic charge isomers on isoelectric focusing, are eluted similarly from four different high-performance liquid chromatographic columns, have absorption maxima at 435 nm under acid conditions and 354 nm at pH 8.3, and bind oleate. Sinusoidally enriched liver plasma membranes and purified h-FABP{sub PM} have GOT enzymatic activity. Monospecific rabbit antiserum against h-FABP{sub PM} reacts on Western blotting with mGOT, and vice versa. Antisera against both proteins produce plasma membrane immunofluorescence in rat hepatocytes and selectively inhibit the hepatocellular uptake of ({sup 3}H)oleate but not that of ({sup 35}S)sulfobromophthalein or ({sup 14}C)taurocholate. The inhibition of oleate uptake produced by anti-h-FABP{sub PM} can be eliminated by preincubation of the antiserum with mGOT; similarly, the plasma membrane immunofluorescence produced by either antiserum can be eliminated by preincubation with the other antigen. These data suggest that h-FABP{sub PM} and mGOT are closely related.

  10. Effect of the esters of gallic acid on model and human blood platelet membranes studied by Fourier transform infrared spectroscopy.

    PubMed

    Qi, S P; Hu, P R

    1993-06-01

    Gallic acid is one of the components of Chinese herbal drug Radix paeoniae used for promoting blood circulation to remove blood stasis. This paper studied the effects of gallic acid and its esters (e.g. ethyl, propyl, isobutyl and butyl gallate) on model and human blood platelet membranes by FTIR which was used for monitoring the physical state of the acyl chain, interfacial and head group region of the membrane lipid bilayer. From the experimental results it can be seen that the gallic acid and its esters have the modifying function on the pure and cholesterol-containing DPPC model membranes, and have the quantity-effective and structural-effective relationships. In addition, it is discovered that these esters have the modifying effect on the structure of human blood platelet membrane and can reverse the effect of ADP. That the effect of the esters of gallic acid counteracts the effect of cholesterol and ADP on human blood platelet perhaps provides a new explanation of the mechanism of Chinese herbal drugs used for promoting blood circulation to remove blood stasis.

  11. 13,16-Dimethyl octacosanedioic acid (iso-diabolic acid), a common membrane-spanning lipid of Acidobacteria subdivisions 1 and 3.

    PubMed

    Damsté, Jaap S Sinninghe; Rijpstra, W Irene C; Hopmans, Ellen C; Weijers, Johan W H; Foesel, Bärbel U; Overmann, Jörg; Dedysh, Svetlana N

    2011-06-01

    The distribution of membrane lipids of 17 different strains representing 13 species of subdivisions 1 and 3 of the phylum Acidobacteria, a highly diverse phylum of the Bacteria, were examined by hydrolysis and gas chromatography-mass spectrometry (MS) and by high-performance liquid chromatography-MS of intact polar lipids. Upon both acid and base hydrolyses of total cell material, the uncommon membrane-spanning lipid 13,16-dimethyl octacosanedioic acid (iso-diabolic acid) was released in substantial amounts (22 to 43% of the total fatty acids) from all of the acidobacteria studied. This lipid has previously been encountered only in thermophilic Thermoanaerobacter species but bears a structural resemblance to the alkyl chains of bacterial glycerol dialkyl glycerol tetraethers (GDGTs) that occur ubiquitously in peat and soil and are suspected to be produced by acidobacteria. As reported previously, most species also contained iso-C(15) and C(16:1ω7C) as major fatty acids but the presence of iso-diabolic acid was unnoticed in previous studies, most probably because the complex lipid that contained this moiety was not extractable from the cells; it could only be released by hydrolysis. Direct analysis of intact polar lipids in the Bligh-Dyer extract of three acidobacterial strains, indeed, did not reveal any membrane-spanning lipids containing iso-diabolic acid. In 3 of the 17 strains, ether-bound iso-diabolic acid was detected after hydrolysis of the cells, including one branched GDGT containing iso-diabolic acid-derived alkyl chains. Since the GDGT distribution in soils is much more complex, branched GDGTs in soil likely also originate from other (acido)bacteria capable of biosynthesizing these components.

  12. Development of a Low-Cost, Durable Membrane and Membrane Electrode Assemby for Stationary and Mobile Fuel Cell Applications

    SciTech Connect

    Michel Foure; Gaboury, Scott; Goldbach, Jim; Mountz, David; Yi, Jung

    2008-01-31

    The development of low cost, durable membranes and membranes electrode assemblies (MEAs) remain a critical challenge for the successful introduction of fuel cells into mass markets. It was the goal of the team lead by Arkema, Inc. (formerly Atofina, Inc.) to address these shortages. Thus, this project addresses the following technical barriers from the Fuel Cells section of the Hydrogen Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan: (A) Durability (B) Cost Arkema’s approach consisted in using blends of polyvinylidenefluoride (PVDF) and proprietary sulfonated polyelectrolytes. The strength and originality of Arkema’s approach lies in the decoupling of ion conductivity from the other requirements. Kynar® (Arkema trade name for PVDF) provides an exceptional combination of properties that make it ideally suited for a membrane matrix. In a first phase, Arkema demonstrated the feasibility of the concept with the M31 membrane generation. After MEA optimization, it was shown that the beginning-of-life (BOL) performance of M31 MEAs was essentially on a par with that of PFSA MEAs at 60ºC under fully humidified conditions. On the other hand, long-term durability studies showed a high decay rate of 45µV/h over a 2100 hr. test. Arkema then designed several families of polyelectrolyte candidates, which, in principle, could not undergo the same failure mechanisms. A new membrane candidate was developed: M41. It offered the same generally good mechanical, ex-situ conductivity and gas barrier properties as M31. In addition, ex-situ accelerated testing suggested a several orders of magnitude improvement in chemical stability. M41 based MEAs showed comparable BOL performance with that of PFSA (80ºC, 100% RH). M41 MEAs were further shown to be able to withstand several hours temperature excursions at 120ºC without apparent damage. Accelerated studies were carried out using the DOE and/or US Fuel Cell Council

  13. Measuring distances between TRPV1 and the plasma membrane using a noncanonical amino acid and transition metal ion FRET

    PubMed Central

    Gordon, Moshe T.; Senning, Eric N.; Munari, Mika A.

    2016-01-01

    Despite recent advances, the structure and dynamics of membrane proteins in cell membranes remain elusive. We implemented transition metal ion fluorescence resonance energy transfer (tmFRET) to measure distances between sites on the N-terminal ankyrin repeat domains (ARDs) of the pain-transducing ion channel TRPV1 and the intracellular surface of the plasma membrane. To preserve the native context, we used unroofed cells, and to specifically label sites in TRPV1, we incorporated a fluorescent, noncanonical amino acid, L-ANAP. A metal chelating lipid was used to decorate the plasma membrane with high-density/high-affinity metal-binding sites. The fluorescence resonance energy transfer (FRET) efficiencies between L-ANAP in TRPV1 and Co2+ bound to the plasma membrane were consistent with the arrangement of the ARDs in recent cryoelectron microscopy structures of TRPV1. No change in tmFRET was observed with the TRPV1 agonist capsaicin. These results demonstrate the power of tmFRET for measuring structure and rearrangements of membrane proteins relative to the cell membrane. PMID:26755770

  14. Weighted-support vector machines for predicting membrane protein types based on pseudo-amino acid composition.

    PubMed

    Wang, Meng; Yang, Jie; Liu, Guo-Ping; Xu, Zhi-Jie; Chou, Kuo-Chen

    2004-06-01

    Membrane proteins are generally classified into the following five types: (1) type I membrane proteins, (2) type II membrane proteins, (3) multipass transmembrane proteins, (4) lipid chain-anchored membrane proteins and (5) GPI-anchored membrane proteins. Prediction of membrane protein types has become one of the growing hot topics in bioinformatics. Currently, we are facing two critical challenges in this area: first, how to take into account the extremely complicated sequence-order effects, and second, how to deal with the highly uneven sizes of the subsets in a training dataset. In this paper, stimulated by the concept of using the pseudo-amino acid composition to incorporate the sequence-order effects, the spectral analysis technique is introduced to represent the statistical sample of a protein. Based on such a framework, the weighted support vector machine (SVM) algorithm is applied. The new approach has remarkable power in dealing with the bias caused by the situation when one subset in the training dataset contains many more samples than the other. The new method is particularly useful when our focus is aimed at proteins belonging to small subsets. The results obtained by the self-consistency test, jackknife test and independent dataset test are encouraging, indicating that the current approach may serve as a powerful complementary tool to other existing methods for predicting the types of membrane proteins.

  15. Measuring distances between TRPV1 and the plasma membrane using a noncanonical amino acid and transition metal ion FRET.

    PubMed

    Zagotta, William N; Gordon, Moshe T; Senning, Eric N; Munari, Mika A; Gordon, Sharona E

    2016-02-01

    Despite recent advances, the structure and dynamics of membrane proteins in cell membranes remain elusive. We implemented transition metal ion fluorescence resonance energy transfer (tmFRET) to measure distances between sites on the N-terminal ankyrin repeat domains (ARDs) of the pain-transducing ion channel TRPV1 and the intracellular surface of the plasma membrane. To preserve the native context, we used unroofed cells, and to specifically label sites in TRPV1, we incorporated a fluorescent, noncanonical amino acid, L-ANAP. A metal chelating lipid was used to decorate the plasma membrane with high-density/high-affinity metal-binding sites. The fluorescence resonance energy transfer (FRET) efficiencies between L-ANAP in TRPV1 and Co(2+) bound to the plasma membrane were consistent with the arrangement of the ARDs in recent cryoelectron microscopy structures of TRPV1. No change in tmFRET was observed with the TRPV1 agonist capsaicin. These results demonstrate the power of tmFRET for measuring structure and rearrangements of membrane proteins relative to the cell membrane.

  16. Enhancing antibiofouling performance of Polysulfone (PSf) membrane by photo-grafting of capsaicin derivative and acrylic acid

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Sun, Haijing; Gao, Xueli; Gao, Congjie

    2014-10-01

    Biofouling is a critical issue in membrane water and wastewater treatment. Herein, antibiofouling PSf membrane was prepared by UV-assisted graft polymerization of acrylic acid (AA) and a capsaicin derivative, N-(5-methyl-3-tert-butyl-2-hydroxy benzyl) acrylamide (MBHBA), on PSf membrane. AA and MBHBA were used as hydrophilic monomer and antibacterial monomer separately. The membranes were characterized by FTIR-ATR, contact angle, SEM, AFM, cross-flow filtration unit, antifouling and antibacterial measurements. Verification of MBHBA and AA that photo-chemically grafted onto the PSf membrane surface is confirmed by carbonyl stretching vibration at ∼1655 cm-1 and ∼1730 cm-1, separately. The increasing AA concentration accelerates the graft-polymerization of MBHBA and resulted in a more hydrophilic surface. Consequently, antifouling property of the membranes was improved on a large level. The flux recovery rate can achieve 100% during the cyclic test, which may be attributed to the more hydrophilic and smooth surface, as well as the decreased membrane pore size. Most importantly, the presence of AA in graft co-polymer does not affect the antibacterial activity of MBHBA. That may be induced by the increasing chain length and flexibility of the grafted polymer chains.

  17. All-trans retinoic acid reduces membrane fluidity of human dermal fibroblasts. Assessment by fluorescence redistribution after photobleaching.

    PubMed Central

    Varani, J.; Burmeister, W.; Bleavins, M. R.; Johnson, K.

    1996-01-01

    All-trans retinoic acid (RA) preserves human dermal fibroblast viability and stimulates proliferation in vitro. These effects are mediated, at least in part, by reducing the extracellular Ca2+ requirement. The same concentrations of RA that reduce the extracellular Ca2+ requirement also interrupt movement of Ca 2+ across the fibroblast plasma membrane. Based on these observations, we have examined the effects of RA on membrane properties that could influence Ca2+ movement. Fibroblasts were labeled with 1-acyl-2-(N-4- nitrobenzo-2-oxa-1,3 diazole)-amino-caproyl phosphatidyl-choline (a fluorescent phospholipid analogue) and examined for fluorescence redistribution after photobleaching (FRAP) with a pulse of intense light as a measure of membrane fluidity. Using this approach, we observed that membrane fluidity was higher when the cells were incubated in medium containing a low (sub-optimal) level of extracellular Ca2+ (0.15 mmol/L) than in a medium containing an optimal concentration (1.4 mmol/L). Treatment of the cells with 3 micromol/L RA reduced membrane fluidity of the cells under both high- and low-Ca2+ conditions. These findings demonstrate that RA has a direct effect on the plasma membrane of human dermal fibroblasts. This provides a possible mechanism for the previously identified inhibition of Ca2+ movement across the membrane of the same cells and for the previously identified protective effects against lysis under low-Ca2+ conditions. PMID:8644871

  18. Interaction of P-aminobenzoic acid with normal and sickel erythrocyte membrane: photoaffinity labelling of the binding sites

    SciTech Connect

    Premachandra, B.R.

    1986-03-05

    Electron microscopic studies revealed that P-Amino benzoic acid (PABA) could prevent eichinocytosis of red cells in vitro. Equilibrium binding studies with right side out membrane vesicles (ROV) revealed a similar number of binding sites (1.2-1.4 ..mu..mol/mg) and Kd (1.4-1.6 mM) values for both normal and sickle cell membranes. /sup 14/C-Azide analogue of PABA was synthesized as a photoaffinity label to probe its sites of interaction on the erythrocyte membranes. Competitive binding studies of PABA with its azide indicated that both the compounds share common binding sites on the membrane surface since a 20 fold excess of azide inhibited PABA binding in a linear fashion. The azide was covalently incorporated into the membrane components only upon irradiation (52-35% of the label found in the proteins and the rest in lipids). Electrophoretic analysis of photolabelled ROV revealed that the azide interacts chiefly with Band 3 protein. PABA inhibited both high and low affinity calcium (Ca) binding sites situated on either surface of the membrane in a non-competitive manner; however, Ca binding stimulated by Mg-ATP was not affected. Ca transport into inside out vesicles was inhibited by PABA; but it did not affect the calcium ATP-ase activity. The authors studies suggest that the mechanism of action of PABA is mediated by its interaction with Band 3 protein (anion channel), calcium channel and calcium binding sites of erythrocyte membrane.

  19. Trans Fatty Acid Derived Phospholipids Show Increased Membrane Cholesterol and Reduced Receptor Activation as Compared to Their Cis Analogs

    PubMed Central

    Niu, Shui-Lin; Mitchell, Drake C.; Litman, Burton J.

    2005-01-01

    The consumption of trans fatty acid (TFA) is linked to the elevation of LDL cholesterol and is considered to be a major health risk factor for coronary heart disease. Despite several decades of extensive research on this subject, the underlying mechanism of how TFA modulates serum cholesterol levels remains elusive. In this study, we examined the molecular interaction of TFA-derived phospholipid with cholesterol and the membrane receptor rhodopsin in model membranes. Rhodopsin is a prototypical member of the G-protein coupled receptor family. It has a well-characterized structure and function and serves as a model membrane receptor in this study. Phospholipid–cholesterol affinity was quantified by measuring cholesterol partition coefficients. Phospholipid–receptor interactions were probed by measuring the level of rhodopsin activation. Our study shows that phospholipid derived from TFA had a higher membrane cholesterol affinity than their cis analogues. TFA phospholipid membranes also exhibited a higher acyl chain packing order, which was indicated by the lower acyl chain packing free volume as determined by DPH fluorescence and the higher transition temperature for rhodopsin thermal denaturation. The level of rhodopsin activation was diminished in TFA phospholipids. Since membrane cholesterol level and membrane receptors are involved in the regulation of cholesterol homeostasis, the combination of higher cholesterol content and reduced receptor activation associated with the presence of TFA–phospholipid could be factors contributing to the elevation of LDL cholesterol. PMID:15766276

  20. Plasma membrane fatty acid-binding protein and mitochondrial glutamic-oxaloacetic transaminase of rat liver are related.

    PubMed Central

    Berk, P D; Wada, H; Horio, Y; Potter, B J; Sorrentino, D; Zhou, S L; Isola, L M; Stump, D; Kiang, C L; Thung, S

    1990-01-01

    The hepatic plasma membrane fatty acid-binding protein (h-FABPPM) and the mitochondrial isoenzyme of glutamic-oxaloacetic transaminase (mGOT) of rat liver have similar amino acid compositions and identical amino acid sequences for residues 3-24. Both proteins migrate with an apparent molecular mass of 43 kDa on SDS/polyacrylamide gel electrophoresis, have a similar pattern of basic charge isomers on isoelectric focusing, are eluted similarly from four different high-performance liquid chromatographic columns, have absorption maxima at 435 nm under acid conditions and 354 nm at pH 8.3, and bind oleate with a Ka approximately 1.2-1.4 x 10(7) M-1. Sinusoidally enriched liver plasma membranes and purified h-FABPPM have GOT enzymatic activity; the relative specific activities (units/mg) of the membranes and purified protein suggest that h-FABPPM constitutes 1-2% of plasma membrane protein in the rat hepatocyte. Monospecific rabbit antiserum against h-FABPPM reacts on Western blotting with mGOT, and vice versa. Antisera against both proteins produce plasma membrane immunofluorescence in rat hepatocytes and selectively inhibit the hepatocellular uptake of [3H]oleate but not that of [35S]sulfobromophthalein or [14C]taurocholate. The inhibition of oleate uptake produced by anti-h-FABPPM can be eliminated by preincubation of the antiserum with mGOT; similarly, the plasma membrane immunofluorescence produced by either antiserum can be eliminated by preincubation with the other antigen. These data suggest that h-FABPPM and mGOT are closely related. Images PMID:2185471

  1. Influence of unsaturated fatty acid membrane component on sensitivity of an Escherichia coli fatty acid auxotroph to conditions of nutrient depletion.

    PubMed Central

    Massa, E M; López Vińals, A; Farías, R N

    1988-01-01

    The unsaturated fatty acid auxotroph Escherichia coli AK7 was provided with either oleic acid (cis 18:1) or linolenic acid (cis 18:3) to vary the degree of unsaturation of cell membrane lipids. The susceptibility of oleic acid- and linolenic acid-grown cells to starvation at 37 degrees C in 154 mM NaCl was compared following the decline in the number of CFU by plating the cells on agar medium. The decline in CFU was faster for linolenic acid-than for oleic acid-grown cells, but it was not indicative of cell death, since culturable CFU was recovered after respirable substrate was added to the starved cell suspension. Cell envelope microviscosity (determined by fluorescence polarization) of oleic acid- and linolenic acid-grown cells was equal in the presence of a respirable substrate, but in its absence the microviscosity of linolenic acid-grown cells was lower than that of oleic acid-grown cells. The results suggest that cell envelope microviscosity is an important factor in determining the sensitivity of E. coli to conditions of nutrient depletion. PMID:3052298

  2. THE INTEGRITY OF THE α-HELICAL DOMAIN OF INTESTINAL FATTY ACID BINDING PROTEIN IS ESSENTIAL FOR THE COLLISION-MEDIATED TRANSFER OF FATTY ACIDS TO PHOSPHOLIPID MEMBRANES

    PubMed Central

    Franchini, G. R.; Storch, J.; Corsico, B.

    2015-01-01

    Summary Intestinal FABP (IFABP) and liver FABP (LFABP), homologous proteins expressed at high levels in intestinal absorptive cells, employ markedly different mechanisms of fatty acid transfer to acceptor model membranes. Transfer from IFABP occurs during protein-membrane-collisional interactions, while for LFABP transfer occurs by diffusion through the aqueous phase. In addition, transfer from IFABP is markedly faster than from LFABP. The overall goal of this study was to further explore the structural differences between IFABP and LFABP which underlie their large functional differences in ligand transport. In particular, we addressed the role of the αI-helix domain in the unique transport properties of intestinal FABP. A chimeric protein was engineered with the ‘body’ (ligand binding domain) of IFABP and the αI-helix of LFABP (α(I)LβIFABP), and the fatty acid transfer properties of the chimeric FABP were examined using a fluorescence resonance energy transfer assay. The results showed a significant decrease in the absolute rate of FA transfer from α(I)LβIFABP compared to IFABP. The results indicate that the αI-helix is crucial for IFABP collisional FA transfer, and further indicate the participation of the αII-helix in the formation of a protein-membrane “collisional complex”. Photo-crosslinking experiments with a photoactivable reagent demonstrated the direct interaction of IFABP with membranes and further supports the importance of the αI helix of IFABP in its physical interaction with membranes. PMID:18284926

  3. Uptake of 4-chloro-2-methylphenoxyacetic acid (MCPA) from the apical membrane of Caco-2 cells by the monocarboxylic acid transporter

    SciTech Connect

    Kimura, Osamu; Tsukagoshi, Kensuke; Endo, Tetsuya

    2008-03-15

    The cellular uptake mechanism of 4-chloro-2-methylphenoxyacetic acid (MCPA), a phenoxyacetic acid derivative, was investigated using Caco-2 epithelial cells. The cells were incubated with 50 {mu}M MCPA at pH 6.0 and 37 deg. C, and the uptake of MCPA from the apical membranes was measured. The uptake of MCPA was significantly decreased by incubation at low temperature (4 {sup o}C) and markedly increased by lowering the extracellular pH. Pretreatment with a protonophore, carbonylcyanide-p-(trifluoromethoxy)phenylhydrazone (25 {mu}M), or metabolic inhibitors, 2,4-dinitrophenol (1 mM) and sodium azide (10 mM), significantly decreased the uptake of MCPA by 53%, 45% and 48%, respectively. Coincubation of MCPA with 10 mM L-lactic acid or {alpha}-cyano-4-hydroxycinnamate, which is a substrate or an inhibitor of the monocarboxylic acid transporters (MCTs), significantly decreased the uptake of MCPA by 31% and 20%, respectively, and coincubation with benzoic acid profoundly decreased the uptake by 68%. In contrast, coincubation with succinic acid (a dicarboxylic acid) did not affect the uptake. Kinetic analysis of initial MCPA uptake suggested that MCPA is taken up via a carrier-mediated process [K{sub m} = 1.37 {+-} 0.15 mM, V{sub max} = 115 {+-} 6 nmol (mg protein){sup -1} (3 min){sup -1}]. Lineweaver-Burk plots show that benzoic acid competitively inhibits the uptake of MCPA with a K{sub i} value of 4.68 {+-} 1.76 mM. A trans-stimulation effect on MCPA uptake was found in cells preloaded with benzoic acid. These results suggest that the uptake of MCPA from the apical membrane of Caco-2 cells is mainly mediated by common MCTs along with benzoic acid but also in part by L-lactic acid.

  4. Cell membrane fatty acid changes and desaturase expression of Saccharomyces bayanus exposed to high pressure homogenization in relation to the supplementation of exogenous unsaturated fatty acids

    PubMed Central

    Serrazanetti, Diana I.; Patrignani, Francesca; Russo, Alessandra; Vannini, Lucia; Siroli, Lorenzo; Gardini, Fausto; Lanciotti, Rosalba

    2015-01-01

    Aims: The aim of this work was to study the responses of Saccharomyces bayanus cells exposed to sub-lethal high-pressure homogenization (HPH) and determine whether the plasmatic membrane can sense HPH in the presence, or absence, of exogenous unsaturated fatty acids (UFAs) in the growth medium. Methods and Results: High-pressure homogenization damaged and caused the collapse of cell walls and membranes of a portion of cells; however, HPH did not significantly affect S. bayanus cell viability (less than 0.3 Log CFU ml-1). HPH strongly affected the membrane fatty acid (FA) composition by increasing the percentage of total UFA when compared with saturated fatty acids. The gene expression showed that the transcription of OLE1, ERG3, and ERG11 increased after HPH. The presence of exogenous UFA abolished HPH-induced effects on the OLE1 and ERG3 genes, increased the percentage of membrane lipids and decreased the expression of OLE1 and ERG3 within 30 min of treatment. Conclusion: The results suggest a key role for UFA in the microbial cell response to sub-lethal stress. In addition, these data provide insight into the molecular basis of the response of S. bayanus to this innovative technology. Significance and Impact of the Study: Elucidation of the mechanism of action for sub-lethal HPH will enable the utilization of this technology to modulate the starter performance at the industrial scale. PMID:26528258

  5. Fatty acid fouling of forward osmosis membrane: Effects of pH, calcium, membrane orientation, initial permeate flux and foulant composition.

    PubMed

    Zhao, Pin; Gao, Baoyu; Yue, Qinyan; Liu, Pan; Shon, Ho Kyong

    2016-08-01

    Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling.

  6. Fatty acid fouling of forward osmosis membrane: Effects of pH, calcium, membrane orientation, initial permeate flux and foulant composition.

    PubMed

    Zhao, Pin; Gao, Baoyu; Yue, Qinyan; Liu, Pan; Shon, Ho Kyong

    2016-08-01

    Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling. PMID:27521936

  7. Permeation of aldopentoses and nucleosides through fatty acid and phospholipid membranes: implications to the origins of life.

    PubMed

    Wei, Chenyu; Pohorille, Andrew

    2013-02-01

    Permeation of aldopentoses and nucleosides through fatty acid and phospholipid membranes was investigated by way of molecular dynamics simulations. Calculated permeability coefficients of membranes to aldopentoses, which exist predominantly in the pyranose form, are in a very good agreement with experimental results. The unexpected preferential permeation of ribose, compared to its diastereomers, found by Sacerdote and Szostak, is explained in terms of inter- and intramolecular interactions involving hydroxyl groups. In aqueous solution, these groups favor the formation of intermolecular hydrogen bonds with neighboring water molecules. Inside the membrane, however, they form intramolecular hydrogen bonds, which in ribose are arranged in a chain. In its diastereomers this chain is broken, which yields higher free energy barrier to transfer through membranes. Faster permeation of ribose would lead to its preferential accumulation inside cells if sugars were converted sufficiently quickly to nonpermeable derivatives. An estimate for the rate of such reaction was derived. Preferential accumulation of ribose would increase the probability of correct monomers' incorporation during synthesis of nucleic acids inside protocells. The same mechanism does not apply to nucleosides or their activated derivatives because sugars are locked in the furanose form, which contains fewer exocyclic hydroxyl groups than does pyranose. The results of this study underscore concerted early evolution of membranes and the biochemical processes that they encapsulated. PMID:23397957

  8. Phosphatidic acid mediates the targeting of tBid to induce lysosomal membrane permeabilization and apoptosis[S

    PubMed Central

    Zhao, Kai; Zhou, Hejiang; Zhao, Xingyu; Wolff, Dennis W.; Tu, Yaping; Liu, Huili; Wei, Taotao; Yang, Fuyu

    2012-01-01

    Upon apoptotic stimuli, lysosomal proteases, including cathepsins and chymotrypsin, are released into cytosol due to lysosomal membrane permeabilization (LMP), where they trigger apoptosis via the lysosomal-mitochondrial pathway of apoptosis. Herein, the mechanism of LMP was investigated. We found that caspase 8-cleaved Bid (tBid) could result in LMP directly. Although Bax or Bak might modestly enhance tBid-triggered LMP, they are not necessary for LMP. To study this further, large unilamellar vesicles (LUVs), model membranes mimicking the lipid constitution of lysosomes, were used to reconstitute the membrane permeabilization process in vitro. We found that phosphatidic acid (PA), one of the major acidic phospholipids found in lysosome membrane, is essential for tBid-induced LMP. PA facilitates the insertion of tBid deeply into lipid bilayers, where it undergoes homo-oligomerization and triggers the formation of highly curved nonbilayer lipid phases. These events induce LMP via pore formation mechanisms because encapsulated fluorescein-conjugated dextran (FD)-20 was released more significantly than FD-70 or FD-250 from LUVs due to its smaller molecular size. On the basis of these data, we proposed tBid-PA interactions in the lysosomal membranes form lipidic pores and result in LMP. We further noted that chymotrypsin-cleaved Bid is more potent than tBid at binding to PA, inserting into the lipid bilayer, and promoting LMP. This amplification mechanism likely contributes to the culmination of apoptotic signaling. PMID:22761256

  9. Plasma membrane H+ and K+ transporters are involved in the weak-acid preservative response of disparate food spoilage yeasts.

    PubMed

    Macpherson, Neil; Shabala, Lana; Rooney, Henrietta; Jarman, Marcus G; Davies, Julia M

    2005-06-01

    The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means; Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H(+). Measurement of H(+) extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae, this yeast uses a plasma membrane H(+)-ATPase to expel H(+) when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H(+) and K(+) fluxes showed that net K(+) influx accompanies net H(+) efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K(+) on long-term exposure to benzoic acid. Analysis of S. cerevisiae K(+) transporter mutants revealed that loss of the high affinity K(+) uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.

  10. Positive effects of salicylic acid pretreatment on the composition of flax plastidial membrane lipids under cadmium stress.

    PubMed

    Belkadhi, Aïcha; De Haro, Antonio; Obregon, Sara; Chaïbi, Wided; Djebali, Wahbi

    2015-01-01

    Interest in use of flax (Linum usitatissimum L.) as cadmium (Cd)-accumulating plant for phytoextraction of contaminated soils opened up a new and promising avenue toward improving tolerance of its varieties and cultivars to Cd stress. The aim of this study is to get insights into the mechanisms of Cd detoxification in cell membranes, by exploring the effects of salicylic acid (SA)-induced priming on fatty acids and lipid composition of flax plantlets, grown for 10 days with 50 and 100 μM Cd. At leaf level, levels of monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), phosphatidylglycerol (PG), and neutral lipids (NL) have shifted significantly in flax plantlets exposed to toxic CdCl2 concentrations, as compared to that of the control. At 100 μM Cd, the linoleic acid (C18:2) decreases mainly in digalactosyldiacylglycerol (DGDG) and all phospholipid species, while linolenic acid (C18:3) declines mostly in MGDG and NL. Conversely, at the highest concentration of the metal, SA significantly enhances the levels of MGDG, PG and phosphatidic acid (PA), and polyunsaturated fatty acids mainly C18:2 and C18:3. Furthermore, SA pretreatment seems to reduce the Cd-induced alterations in both plastidial and extraplastidial lipid classes, but preferentially preserves the plastidial lipids by acquiring higher levels of polyunsaturated fatty acids. These results suggest that flax plantlets pretreated with SA exhibits more stability of their membranes under Cd-stress conditions.

  11. Preparation of mesoporous poly (acrylic acid)/SiO2 composite nanofiber membranes having adsorption capacity for indigo carmine dye

    NASA Astrophysics Data System (ADS)

    Xu, Ran; Jia, Min; Li, Fengting; Wang, Hongtao; Zhang, Bingru; Qiao, Junlian

    2012-03-01

    Mesoporous poly (acrylic acid)/SiO2 (PAA/SiO2) composite nanofiber membranes functionalized with mercapto groups were fabricated by a sol-gel electrospinning method, and their adsorption capacity for indigo carmine was investigated. The membranes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray powder diffraction (XRD), and nitrogen adsorption-desorption measurement. SEM and TEM observation results showed that the PAA/SiO2 fibers had diameters between 400-800 nm and mesopores with an average pore size of 3.88 nm. The specific surface area of the mesoporous nanofiber membranes was 514.89 m2/g. The characteristic peaks for mercapto group vibration in FTIR and Raman spectra demonstrated that the mercapto groups have been incorporated into the silica skeleton. The adsorption isotherm data of indigo carmine on the membranes fit well with Redlich-Peterson model, and the maximum adsorption capacity calculated was 523.11 mg/g. It was found that the removal rate of indigo carmine by the membranes reached a maximum of 98% in 90 min and the adsorption kinetics followed a pseudo-second-order model. The high adsorption capacity of PAA/SiO2 nanofiber membrane makes it a promising adsorbent for indigo carmine removal from the wastewater.

  12. Superhydrophilic poly(L-lactic acid) electrospun membranes for biomedical applications obtained by argon and oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Correia, D. M.; Ribeiro, C.; Botelho, G.; Borges, J.; Lopes, C.; Vaz, F.; Carabineiro, S. A. C.; Machado, A. V.; Lanceros-Méndez, S.

    2016-05-01

    Poly(L-lactic acid), PLLA, electrospun membranes and films were plasma treated at different times and power with argon (Ar) and oxygen (O2), independently, in order to modify the hydrophobic nature of the PLLA membranes. Both Ar and O2 plasma treatments promote an increase in fiber average size of the electrospun membranes from 830 ± 282 nm to 866 ± 361 and 1179 ± 397 nm, respectively, for the maximum exposure time (970 s) and power (100 W). No influence of plasma treatment was detected in the physical-chemical characteristics of PLLA, such as chemical structure, polymer phase or degree of crystallinity. On the other hand, an increase in the roughness of the films was obtained both with argon and oxygen plasma treatments. Surface wettability studies revealed a decrease in the contact angle with increasing plasma treatment time for a given power and with increasing power for a given time in membranes and films and superhydrophilic electrospun fiber membranes were obtained. Results showed that the argon and oxygen plasma treatments can be used to tailor hydrophilicity of PLLA membranes for biomedical applications. MTT assay results indicated that plasma treatments under Ar and O2 do not influence the metabolic activity of MC3T3-E1 pre-osteoblast cells.

  13. First observation of amino acid side chain dynamics in membrane proteins using high field deuterium nuclear magnetic resonance spectroscopy

    SciTech Connect

    Kinsey, R.A.; Kintanar, A.; Tsai, M.D.; Smith, R.L.; Janes, N.; Oldfield, E.

    1981-05-10

    The first deuterium NMR spectra of an individual membrane protein, bacteriohodopsin in the purple membrane of Halobacterium halobium R1 has been obtained. Biosynthetic isotopic enrichment with (gamma-2H6) valine and high field Fourier transform operation permitted rapid data acquisition on intact membranes, including measurement of relaxation times. At some temperatures high quality spectra could be obtained in less than 1 s. (U-14C)Valine tracer studies indicate that less than or equal to 2% of valine added to the growth medium is broken down and incorporated into other membrane constituents. The NMR results indicate that the valine side chain is a rather rigid structure. Motion about C alpha-C beta is slow (less than 10(5) s-1) at growth temperature, while motion about C beta-C gamma is as expected fast (much greater than 10(5) s-1) at all accessible temperatures. The activation energy for methyl group rotation from spin-lattice relaxation data between -75 and 53 degrees C is approximately 2.4 kcal/mol, in good agreement with previous 1H NMR studies on solid alkanes. Preliminary data on (gamma-2H6)valine-labeled Acholeplasma laidlawii B (PG9) cell membranes are also presented. Results strongly suggest that it should now be possible to observe in great detail the motions of any type of amino acid side chain in membrane proteins, including the effects of lipid composition on protein dynamics.

  14. Lipophilic and polar interaction forces between acidic drugs and membrane phospholipids encoded in IAM-HPLC indexes: their role in membrane partition and relationships with BBB permeation data.

    PubMed

    Grumetto, Lucia; Carpentiero, Carmen; Di Vaio, Paola; Frecentese, Francesco; Barbato, Francesco

    2013-03-01

    The membrane phospholipid affinity data, log k(w)(IAM), for 18 acidic and unionized drugs spanning a wide lipophilicity range were measured by HPLC on two different phospholipid stationary phases, i.e. IAM.PC.MG and IAM.PC.DD2. These data related weakly with both log P(N) values, the n-octanol/water partition coefficients of the neutral forms, and log D(7.4) values, the n-octanol/water partition coefficients of the mixtures of neutral and ionized forms at pH 7.4. The lack of collinearity confirms that, differently from partition in n-octanol/water, partition in phospholipids encodes not only lipophilic/hydrophobic intermolecular recognition forces but also ionic bonds, due to electrostatic interactions between electrically charged species and phospholipids, according to the "pH piston hypothesis". Since, differently from bases, electrostatic interactions between acids and phospholipids take place at the surface of phospholipid layers (choline moieties), and not near their lipophilic core (phosphate moieties), they were parameterized by a new procedure yielding "Δ'log k(w)(IAM)" parameters, i.e. the difference between the IAM retention factors observed for the analytes and those of neutral compounds with the same n-octanol partition values displayed by the analytes at pH 7.4. All acidic analytes, but one, and all unionized analytes, but the unionizable ones, showed positive Δ'log k(w)(IAM) values, indicating that they partition stronger in phospholipids than in n-octanol. Log BB values (capability to pass BBB) weakly related with both lipophilicity and phospholipid affinity values; in contrast they are inversely related with Δ'log k(w)(IAM) values. The relationships between log BB and Δ'log k(w)(IAM) practically overlapped the previously found log BB/Δlog k(w)(IAM) relationships for bases. The excess of polar interaction component between acidic drugs and phospholipids, mainly electrostatic forces, although enhancing partition in phospholipids, hinders membrane

  15. Peroxynitrous acid induces structural and functional modifications to basement membranes and its key component, laminin.

    PubMed

    Degendorfer, Georg; Chuang, Christine Y; Hammer, Astrid; Malle, Ernst; Davies, Michael J

    2015-12-01

    Basement membranes (BM) are specialized extracellular matrices underlying endothelial cells in the artery wall. Laminin, the most abundant BM glycoprotein, is a structural and biologically active component. Peroxynitrous acid (ONOOH), a potent oxidizing and nitrating agent, is formed in vivo at sites of inflammation from superoxide and nitric oxide radicals. Considerable data supports ONOOH formation in human atherosclerotic lesions, and an involvement of this oxidant in atherosclerosis development and lesion rupture. These effects may be mediated, at least in part, via extracellular matrix damage. In this study we demonstrate co-localization of 3-nitrotyrosine (a product of tyrosine damage by ONOOH) and laminin in human atherosclerotic lesions. ONOOH-induced damage to BM was characterized for isolated murine BM, and purified murine laminin-111. Exposure of laminin-111 to ONOOH resulted in dose-dependent loss of protein tyrosine and tryptophan residues, and formation of 3-nitrotyrosine, 6-nitrotryptophan and the cross-linked material di-tyrosine, as detected by amino acid analysis and Western blotting. These changes were accompanied by protein aggregation and fragmentation as detected by SDS-PAGE. Endothelial cell adhesion to isolated laminin-111 exposed to 10 μM or higher levels of ONOOH was significantly decreased (~25%) compared to untreated controls. These data indicate that laminin is oxidized by equimolar or greater concentrations of ONOOH, with this resulting in structural and functional changes. These modifications, and resulting compromised cell-matrix interactions, may contribute to endothelial cell dysfunction, a weakening of the structure of atherosclerotic lesions, and an increased propensity to rupture.

  16. Triiodothyronine activates lactate oxidation without impairing fatty acid oxidation and improves weaning from extracorporeal membrane oxygenation

    SciTech Connect

    Kajimoto, Masaki; Ledee, Dolena R.; Xu, Chun; Kajimoto, Hidemi; Isern, Nancy G.; Portman, Michael A.

    2014-01-01

    Background: Extracorporeal membrane oxygenation (ECMO) provides a rescue for children with severe cardiac failure. We previously showed that triiodothyronine (T3) improves cardiac function by modulating pyruvate oxidation during weaning. This study was focused on fatty acid (FA) metabolism modulated by T3 for weaning from ECMO after cardiac injury. Methods: Nineteen immature piglets (9.1-15.3 kg) were separated into 3 groups with ECMO (6.5 hours) and wean: normal circulation (Group-C);transient coronary occlusion (10 minutes) followed by ECMO (Group-IR); and IR with T3 supplementation (Group-IR-T3). 13-Carbon labeled lactate, medium-chain and long-chain FAs were infused as oxidative substrates. Substrate fractional contribution to the citric acid cycle (FC) was analyzed by 13-Carbon nuclear magnetic resonance. Results: ECMO depressed circulating T3 levels to 40% baseline at 4 hours and were restored in Group-IR-T3. Group-IR decreased cardiac power, which was not fully restorable and 2 pigs were lost because of weaning failure. Group-IR also depressed FC-lactate, while the excellent contractile function and energy efficiency in Group-IR-T3 occurred along with a marked FC-lactate increase and [ATP]/[ADP] without either decreasing FC-FAs or elevating myocardial oxygen consumption over Group-C or -IR. Conclusions: T3 releases inhibition of lactate oxidation following ischemia-reperfusion injury without impairing FA oxidation. These findings indicate that T3 depression during ECMO is maladaptive, and that restoring levels improves metabolic flux and enhances contractile function during weaning.

  17. Association of the pr Peptides with Dengue Virus at Acidic pH Blocks Membrane Fusion

    SciTech Connect

    Yu, I.-M.; Holdaway, H.A.; Chipman, P.R.; Kuhn, R.J.; Rossmann, M.G.; Chen, J.; Purdue

    2010-07-27

    Flavivirus assembles into an inert particle that requires proteolytic activation by furin to enable transmission to other hosts. We previously showed that immature virus undergoes a conformational change at low pH that renders it accessible to furin (I. M. Yu, W. Zhang, H. A. Holdaway, L. Li, V. A. Kostyuchenko, P. R. Chipman, R. J. Kuhn, M. G. Rossmann, and J. Chen, Science 319:1834-1837, 2008). Here we show, using cryoelectron microscopy, that the structure of immature dengue virus at pH 6.0 is essentially the same before and after the cleavage of prM. The structure shows that after cleavage, the proteolytic product pr remains associated with the virion at acidic pH, and that furin cleavage by itself does not induce any major conformational changes. We also show by liposome cofloatation experiments that pr retention prevents membrane insertion, suggesting that pr is present on the virion in the trans-Golgi network to protect the progeny virus from fusion within the host cell.

  18. Kinetics of phenolic and phthalic acid esters biodegradation in membrane bioreactor (MBR) treating municipal landfill leachate.

    PubMed

    Boonnorat, Jarungwit; Chiemchaisri, Chart; Chiemchaisri, Wilai; Yamamoto, Kazuo

    2016-05-01

    The kinetic of phenolic and phthalic acid esters (PAEs) biodegradation in membrane bioreactor (MBR) treating municipal landfill leachate was investigated. Laboratory-scale MBR was fed with mixture of fresh and stabilized landfill leachate containing carbon to nitrogen (C/N) ratio of 10, 6, 3 and operated under different solid retention time (SRT) of 90, 15 and 5 d. Batch experiments using MBR sludge obtained from each steady-state operating condition revealed highest biodegradation rate constant (k) of 0.059-0.092 h(-1) of the phenolic and PAEs compounds at C/N of 6. Heterotrophic bacteria were the major group responsible for biodegradation of compounds whereas the presence of ammonia-oxidizing bacteria (AOB) helped accelerating their removals. Heterotrophic nitrifying bacteria found under high ammonia condition had an important role in enhancing the biodegradation of phenols and PAEs by releasing phenol hydroxylase (PH), esterase (EST) and phthalate dioxygenase (PDO) enzymes and the presence of AOB helped improving biodegradation of phenolic and PAEs compounds through their co-metabolism. PMID:26908045

  19. Extracorporeal membrane oxygenation promotes long chain fatty acid oxidation in the immature swine heart in vivo

    PubMed Central

    Kajimoto, Masaki; O’Kelly Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy; Olson, Aaron K.; Portman, Michael A.

    2013-01-01

    Extracorporeal membrane oxygenation (ECMO) supports infants and children with severe cardiopulmonary compromise. Nutritional support for these children includes provision of medium- and long-chain fatty acids (FAs). However, ECMO induces a stress response, which could limit the capacity for FA oxidation. Metabolic impairment could induce new or exacerbate existing myocardial dysfunction. Using a clinically relevant piglet model, we tested the hypothesis that ECMO maintains the myocardial capacity for FA oxidation and preserves myocardial energy state. Provision of 13-Carbon labeled medium-chain FA (octanoate), long-chain free FAs (LCFAs), and lactate into systemic circulation showed that ECMO promoted relative increases in myocardial LCFA oxidation while inhibiting lactate oxidation. Loading of these labeled substrates at high dose into the left coronary artery demonstrated metabolic flexibility as the heart preferentially oxidized octanoate. ECMO preserved this octanoate metabolic response, but also promoted LCFA oxidation and inhibited lactate utilization. Rapid upregulation of pyruvate dehydrogenase kinase-4 (PDK4) protein appeared to participate in this metabolic shift during ECMO. ECMO also increased relative flux from lactate to alanine further supporting the role for pyruvate dehydrogenase inhibition by PDK4. High dose substrate loading during ECMO also elevated the myocardial energy state indexed by phosphocreatine to ATP ratio. ECMO promotes LCFA oxidation in immature hearts, while maintaining myocardial energy state. These data support the appropriateness of FA provision during ECMO support for the immature heart. PMID:23727393

  20. Metabolism of milk fat globule membrane components by nonstarter lactic acid bacteria isolated from cheese.

    PubMed

    Moe, K M; Porcellato, D; Skeie, S

    2013-02-01

    The objective of this study was to investigate how components present in the milk fat globule membrane (MFGM) may be used for growth and survival by cheese-ripening lactobacilli. This was achieved by analyzing metabolites produced during incubation on appropriate media. The lactobacilli investigated were able to utilize components from the MFGM throughout a 24-d incubation period. We observed an apparent connection between the higher proteolytic activity of Lactobacillus paracasei INF448 and its ability to grow in the MFGM media after depletion of readily available sugars. All the studied strains produced large amounts of acetate when grown on an acylated aminosugar, presumably from deacetylation of the monosaccharides. Growth of Lb. plantarum INF15D on D-galactose resulted in a metabolic shift, expressed as different fates of the produced pyruvate, compared with growth on the other monosaccharides. For Lb. plantarum INF15D, the presence of D-galactose also seemed to initiate degradation of some amino acids known to take part in energy production, specifically Arg and Tyr.

  1. Extracorporeal membrane oxygenation promotes long chain fatty acid oxidation in the immature swine heart in vivo

    SciTech Connect

    Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy G.; Olson, Aaron; Portman, Michael A.

    2013-09-01

    Extracorporeal membrane oxygenation (ECMO) supports infants and children with severe cardiopulmonary compromise. Nutritional support for these children includes provision of medium- and long-chain fatty acids (FAs). However, ECMO induces a stress response, which could limit the capacity for FA oxidation. Metabolic impairment could induce new or exacerbate existing myocardial dysfunction. Using a clinically relevant piglet model, we tested the hypothesis that ECMO maintains the myocardial capacity for FA oxidation and preserves myocardial energy state. Provision of 13-Carbon labeled medium-chain FA (octanoate), longchain free FAs (LCFAs), and lactate into systemic circulation showed that ECMO promoted relative increases in myocardial LCFA oxidation while inhibiting lactate oxidation. Loading of these labeled substrates at high dose into the left coronary artery demonstrated metabolic flexibility as the heart preferentially oxidized octanoate. ECMO preserved this octanoate metabolic response, but also promoted LCFA oxidation and inhibited lactate utilization. Rapid upregulation of pyruvate dehydrogenase kinase-4 (PDK4) protein appeared to participate in this metabolic shift during ECMO. ECMO also increased relative flux from lactate to alanine further supporting the role for pyruvate dehydrogenase inhibition by PDK4. High dose substrate loading during ECMO also elevated the myocardial energy state indexed by phosphocreatine to ATP ratio. ECMO promotes LCFA oxidation in immature hearts, while maintaining myocardial energy state. These data support the appropriateness of FA provision during ECMO support for the immature heart.

  2. Effect of polyunsaturated fatty acids and phospholipids on ( sup 3 H)-vitamin E incorporation into pulmonary artery endothelial cell membranes

    SciTech Connect

    Sekharam, K.M.; Patel, J.M.; Block, E.R. )

    1990-12-01

    Vitamin E, a dietary antioxidant, is presumed to be incorporated into the lipid bilayer of biological membranes to an extent proportional to the amount of polyunsaturated fatty acids or phospholipids in the membrane. In the present study we evaluated the distribution of incorporated polyunsaturated fatty acids (PUFA) and phosphatidylethanolamine (PE) in various membranes of pulmonary artery endothelial cells. We also studied whether incorporation of PUFA or PE is responsible for increased incorporation of (3H)-vitamin E into the membranes of these cells. Following a 24-hr incubation with linoleic acid (18:2), 18:2 was increased by 6.9-, 9.2-, and 13.2-fold in plasma, mitochondrial, and microsomal membranes, respectively. Incorporation of 18:2 caused significant increases in the unsaturation indexes of mitochondrial and microsomal polyunsaturated fatty acyl chains (P less than .01 versus control in both membranes). Incubation with arachidonic acid (20:4) for 24 hr resulted in 1.5-, 2.3-, and 2.4-fold increases in 20:4 in plasma, mitochondrial, and microsomal membranes, respectively. The unsaturation indexes of polyunsaturated fatty acyl chains of mitochondrial and microsomal membranes also increased (P less than .01 versus control in both membranes). Although incubations with 18:2 or 20:4 resulted in several-fold increases in membrane 18:2 or 20:4 fatty acids, incorporation of (3H)-vitamin E into these membranes was similar to that in controls. Following a 24-hr incubation with PE, membrane PE content was significantly increased, and (3H)-vitamin E incorporation was also increased to a comparable degree, i.e., plasma membrane greater than mitochondria greater than microsomes. Endogenous vitamin E content of the cells was not altered because of increased incorporation of PE and (3H)-vitamin E.

  3. Characterization of Hybrid Polyhedral Oligomeric Silsesquioxane (POSS)-Polybenzimidazole (PBI)-Phosphoric Acid (PA) Materials Intended for Proton Exchange Membranes (PEM)

    NASA Astrophysics Data System (ADS)

    Bubeck, Robert; Stark, Edmund; Decker, Berryinne; Hartmann-Thompson, Claire

    2013-03-01

    Isophthalic acid and 3,3'-diaminobenzidine (DAB) were polymerized in the presence of polyphosphoric acid (PPA) and various additives, degree of polymerization was monitored by viscosity and torque change measurements, and membranes were prepared by casting the reaction solution and allowing PPA to hydrolyze to PA under ambient conditions. As a function of relative humidity, the membranes were characterized for (1) acid content, (2) in-plane conductivity and (3) complex shear modulus G* obtained via oscillatory parallel plate dynamic mechanical spectroscopy. The addition of sulfonated octaphenyl polyhedral oligomeric silsesquixane (S-POSS) to m-polybenzimidazole (PBI)-phosphoric acid (PA) membranes resulted in increased in-plane proton conductivity at high temperatures (120-150 °C) and increased G* relative to a m-PBI control membrane and to m-PBI control membranes carrying comparable weight loadings of non-proton conducting octaphenyl-POSS nanoadditive or silica.

  4. Water transport in water-in-oil-in-water liquid emulsion membrane system for the separation of lactic acid

    SciTech Connect

    Mok, Y.S.; Lee, W.K. )

    1994-03-01

    Liquid emulsion membranes (LEMs) were applied to the separation of lactic acid from an aqueous feed phase, and water transport (swelling) was investigated during the separation. Considering that as lactic acid was extracted into the internal stripping phase, osmotic pressure difference across the membrane was varied, the water transfer coefficient was evaluated. The water transfer coefficient was larger at higher carrier concentration and initial lactic acid concentration, which means that emulsion swelling can also be mediated by solute/carrier complexes although it is, in general, osmotically induced. The appropriate LEM formulation was given for separation and concentration of lactic acid. If both separation and concentration are desired, evidently emulsion swelling should be considered in conjunction with the transport rate of lactic acid. It was observed that the separated solute concentration in the internal phase was lowered due to swelling during the operation. Nevertheless, lactic acid could be concentrated in the internal phase more than 6 times in specific conditions, indicating that as the volume ratio of external phase to internal phase is increased, a still higher concentration in the internal phase can be obtained. 22 refs., 10 figs., 4 tabs.

  5. Modification of Fatty acids in membranes of bacteria: implication for an adaptive mechanism to the toxicity of carbon nanotubes.

    PubMed

    Zhu, Baotong; Xia, Xinghui; Xia, Na; Zhang, Shangwei; Guo, Xuejun

    2014-04-01

    We explored whether bacteria could respond adaptively to the presence of carbon nanotubes (CNTs) by investigating the influence of CNTs on the viability, composition of fatty acids, and cytoplasmic membrane fluidity of bacteria in aqueous medium for 24 h exposure. The CNTs included long single-walled carbon nanotubes (L-SWCNTs), short single-walled carbon nanotubes (S-SWCNTs), short carboxyl single-walled carbon nanotubes (S-SWCNT-COOH), and aligned multiwalled carbon nanotubes (A-MWCNTs). The bacteria included three common model bacteria, Staphyloccocus aureus (Gram-positive), Bacillus subtilis (Gram-positive), and Escherichia coli (Gram-negative), and one polybrominated diphenyl ether degrading strain, Ochrobactrum sp. (Gram-negative). Generally, L-SWCNTs were the most toxic to bacteria, whereas S-SWCNT-COOH showed the mildest bacterial toxicity. Ochrobactrum sp. was more susceptible to the toxic effect of CNTs than E. coli. Compared to the control in the absence of CNTs, the viability of Ochrobactrum sp. decreased from 71.6-81.4% to 41.8-70.2%, and E. coli from 93.7-104.0% to 67.7-91.0% when CNT concentration increased from 10 to 50 mg L(-1). The cytoplasmic membrane fluidity of bacteria increased with CNT concentration, and a significant negative correlation existed between the bacterial viabilities and membrane fluidity for E. coli and Ochrobactrum sp. (p < 0.05), indicating that the increase in membrane fluidity induced by CNTs was an important factor causing the inactivation of bacteria. In the presence of CNTs, E. coli and Ochrobactrum sp. showed elevation in the level of saturated fatty acids accompanied with reduction in unsaturated fatty acids, compensating for the fluidizing effect of CNTs. This demonstrated that bacteria could modify their composition of fatty acids to adapt to the toxicity of CNTs. In contrast, S. aureus and B. subtilis exposed to CNTs increased the proportion of branched-chain fatty acids and decreased the level of straight

  6. ΔpH-Dependent Amino Acid Transport into Plasma Membrane Vesicles Isolated from Sugar Beet (Beta vulgaris L.) Leaves

    PubMed Central

    Li, Zhen-Chang; Bush, Daniel R.

    1991-01-01

    Proton-coupled aliphatic, neutral amino acid transport was investigated in plasma membrane vesicles isolated from sugar beet (Beta vulgaris L., cv Great Western) leaves. Two neutral amino acid symport systems were resolved based on inter-amino acid transport competition and on large variations in the specific activity of each porter in different species. Competitive inhibition was observed for transport competition between alanine, methionine, glutamine, and leucine (the alanine group) and between isoleucine, valine, and threonine (the isoleucine group). The apparent Km and Ki values were similar for transport competition among amino acids within the alanine group. In contrast, the kinetics of transport competition between these two groups of amino acids did not fit a simple competitive model. Furthermore, members of the isoleucine group were weak transport antagonists of the alanine group. These results are consistent with two independent neutral amino acid porters. In support of that conclusion, the ratio of the specific activity of alanine transport versus isoleucine transport varied from two- to 13-fold in plasma membrane vesicles isolated from different plant species. This ratio would be expected to remain relatively stable if these amino acids were moving through a single transport system and, indeed, the ratio of alanine to glutamine transport varied less than twofold. Analysis of the predicted structure of the aliphatic, neutral amino acids in solution shows that isoleucine, valine, and threonine contain a branched methyl or hydroxyl group at the β-carbon position that places a dense electron cloud close to the α-amino group. This does not occur for the unbranched amino acids or those that branch further away, e.g. leucine. We hypothesize that this structural feature of isoleucine, valine, and threonine results in unfavorable steric interactions with the alanine transport system that limits their flux through this porter. Hydrophobicity and hydrated

  7. ELECTROCHEMICAL PROPERTIES, MECHANICAL TESTING, AND GEL MORPHOLOGY STUDY OF PHOSPHORIC ACID-DOPED META-POLYBENZIMIDAZOLE MEMBRANES VIA CONVENTIONALLY IMBIBING AND THE SOL-GEL PROCESS

    SciTech Connect

    Perry, Kelly A; More, Karren Leslie; Benicewicz, Brian

    2009-01-01

    Proton exchange membrane (PEM) research has been directed at phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes since the 1990s. PEM fuel cells based on PA-doped PBI membranes produced via a sol-gel transition process have achieved lifetimes >10,000hrs with low degradation rates. It has been suggested that the gel morphology of the PA-doped PBI membranes is responsible for their excellent electrochemical performance. Thus, a study has been underway to characterize the microstructure of PA-doped PBI membranes, and to correlate structure with performance. However, PA-doped PBI membranes present special challenges for microscopy analysis, as these membranes are extremely sensitive to the electron beam and high vacuum conditions. This paper will discuss and compare the mechanical, electrochemical, and cryo-SEM analyses of PA-doped meta-PBI membranes produced via conventional imbibing and the sol-gel process.

  8. Manganese accumulation in membrane fractions of primary astrocytes is associated with decreased γ-aminobutyric acid (GABA) uptake, and is exacerbated by oleic acid and palmitate.

    PubMed

    Fordahl, Steve C; Erikson, Keith M

    2014-05-01

    Manganese (Mn) exposure interferes with GABA uptake; however, the effects of Mn on GABA transport proteins (GATs) have not been identified. We sought to characterize how Mn impairs GAT function in primary rat astrocytes. Astrocytes exposed to Mn (500 μM) had significantly reduced (3)H-GABA uptake despite no change in membrane or cytosolic GAT3 protein levels. Co-treatment with 100 μM oleic or palmitic acids (both known to be elevated in Mn neurotoxicity), exacerbated the Mn-induced decline in (3)H-GABA uptake. Mn accumulation in the membrane fraction of astrocytes was enhanced with fatty acid administration, and was negatively correlated with (3)H-GABA uptake. Furthermore, control cells exposed to Mn only during the experimental uptake had significantly reduced (3)H-GABA uptake, and the addition of GABA (50 μM) blunted cytosolic Mn accumulation. These data indicate that reduced GAT function in astrocytes is influenced by Mn and fatty acids accumulating at or interacting with the plasma membrane.

  9. Membrane topology and essential amino acid residues of Phs1, a 3-hydroxyacyl-CoA dehydratase involved in very long-chain fatty acid elongation.

    PubMed

    Kihara, Akio; Sakuraba, Hiroko; Ikeda, Mika; Denpoh, Aki; Igarashi, Yasuyuki

    2008-04-25

    Yeast Phs1 is the 3-hydroxyacyl-CoA dehydratase that catalyzes the third reaction of the four-step cycle in the elongation of very long-chain fatty acids (VLCFAs). In yeast, the hydrophobic backbone of sphingolipids, ceramide, consists of a long-chain base and an amide-linked C26 VLCFA. Therefore, defects in VLCFA synthesis would be expected to greatly affect sphingolipid synthesis. In fact, in this study we found that reduced Phs1 levels result in significant impairment of the conversion of ceramide to inositol phosphorylceramide. Phs1 proteins are conserved among eukaryotes, constituting a novel protein family. Phs1 family members exhibit no sequence similarity to other dehydratase families, so their active site sequence and catalytic mechanism have been completely unknown. Here, by mutating 22 residues conserved among Phs1 family members, we identified six amino acid residues important in Phs1 function, two of which (Tyr-149 and Glu-156) are indispensable. We also examined the membrane topology of Phs1 using an N-glycosylation reporter assay. Our results suggest that Phs1 is a membrane-spanning protein that traverses the membrane six times and has an N terminus and C terminus facing the cytosol. The important amino acids are concentrated in or near two of the six proposed transmembrane regions. Thus, we also propose a catalytic mechanism for Phs1 that is not unlike mechanisms used by other hydratases active in lipid synthesis.

  10. Three-layered absorptive glass mat separator with membrane for application in valve-regulated lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Naidenov, V.; Pavlov, D.; Cherneva, M.

    During charge and discharge of the lead-acid cell equal amounts of H 2SO 4 participate in the reactions at the two types of plates (electrodes). However, the charge and discharge reactions at the positive plates involve also 2 mol of water per every mole of reacted PbO 2. Consequently, a concentration difference appears in the electrolyte between the two electrodes (horizontal stratification), which affects the reversibility of the processes at the two electrodes and thus the cycle life of the battery. The present paper proposes the use of a three-layered absorptive glass mat (AGM) separator, the middle layer playing the role of a membrane that divides (separates) the anodic and cathodic electrolyte spaces, and controls the exchange rates of H 2SO 4, H + ions, O 2 and H 2O flows between the two electrode spaces. To be able to perform this membrane function, the thinner middle AGM layer (0.2 mm) is processed with an appropriate polymeric emulsion to acquire balanced hydrophobic/hydrophilic properties, which sustain constant H 2SO 4 concentration in the two electrode spaces during cycling. Three types of polymeric emulsions have been used for treatment of the membrane: (a) polyvinylpyrollidonestyrene (MPVS), (b) polyvinylpyrrolidone "Luviskol" (MPVP), or (c) polytetrafluorethylene modified with Luviskol (MMAGM). It is established experimentally that the MMAGM membrane maintains equal acid concentration in the anodic and cathodic spaces (no horizontal stratification) during battery cycling and hence ensures longer cycle life performance.

  11. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    PubMed Central

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease. PMID:26796668

  12. Permeation of membranes by the neutral form of amino acids and peptides: relevance to the origin of peptide translocation

    NASA Technical Reports Server (NTRS)

    Chakrabarti, A. C.; Deamer, D. W.; Miller, S. L. (Principal Investigator)

    1994-01-01

    The flux of amino acids and other nutrient solutes such as phosphate across lipid bilayers (liposomes) is 10(5) slower than facilitated inward transport across biological membranes. This suggest that primitive cells lacking highly evolved transport systems would have difficulty transporting sufficient nutrients for cell growth to occur. There are two possible ways by which early life may have overcome this difficulty: (1) The membranes of the earliest cellular life-forms may have been intrinsically more permeable to solutes; or (2) some transport mechanism may have been available to facilitate transbilayer movement of solutes essential for cell survival and growth prior to the evolution of membrane transport proteins. Translocation of neutral species represents one such mechanism. The neutral forms of amino acids modified by methylation (creating protonated weak bases) permeate membranes up to 10(10) times faster than charged forms. This increased permeability when coupled to a transmembrane pH gradient can result in significantly increased rates of net unidirectional transport. Such pH gradients can be generated in vesicles used to model protocells that preceded and were presumably ancestral to early forms of life. This transport mechanism may still play a role in some protein translocation processes (e.g. for certain signal sequences, toxins and thylakoid proteins) in vivo.

  13. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    NASA Astrophysics Data System (ADS)

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

  14. The role of putrescine in the regulation of proteins and fatty acids of thylakoid membranes under salt stress

    PubMed Central

    Shu, Sheng; Yuan, Yinghui; Chen, Jie; Sun, Jin; Zhang, Wenhua; Tang, Yuanyuan; Zhong, Min; Guo, Shirong

    2015-01-01

    Polyamines can alleviate the inhibitory effects of salinity on plant growth by regulating photosynthetic efficiency. However, little information is available to explain the specific mechanisms underlying the contribution of polyamines to salt tolerance of the photosynthetic apparatus. Here, we investigated the role of putrescine (Put) on the photosynthetic apparatus of cucumber seedlings under salt stress. We found that NaCl stress resulted in severe ion toxicity and oxidative stress in cucumber chloroplasts. In addition, salinity caused a significant increase in the saturated fatty acid contents of thylakoid membranes. Put altered unsaturated fatty acid content, thereby alleviating the disintegration of thylakoid grana lamellae and reducing the number of plastoglobuli in thylakoid membranes. BN-PAGE revealed Put up-regulated the expression of ATP synthase, CP47, D1, Qb, and psbA proteins and down-regulated CP24, D2, and LHCII type III in NaCl-stressed thylakoid membranes. qRT-PCR analysis of gene expression was used to compare transcript and protein accumulation among 10 candidate proteins. For five of these proteins, induced transcript accumulation was consistent with the pattern of induced protein accumulation. Our results suggest that Put regulates protein expression at transcriptional and translational levels by increasing endogenous polyamines levels in thylakoid membranes, which may stabilise photosynthetic apparatus under salt stress. PMID:26435404

  15. The role of putrescine in the regulation of proteins and fatty acids of thylakoid membranes under salt stress.

    PubMed

    Shu, Sheng; Yuan, Yinghui; Chen, Jie; Sun, Jin; Zhang, Wenhua; Tang, Yuanyuan; Zhong, Min; Guo, Shirong

    2015-01-01

    Polyamines can alleviate the inhibitory effects of salinity on plant growth by regulating photosynthetic efficiency. However, little information is available to explain the specific mechanisms underlying the contribution of polyamines to salt tolerance of the photosynthetic apparatus. Here, we investigated the role of putrescine (Put) on the photosynthetic apparatus of cucumber seedlings under salt stress. We found that NaCl stress resulted in severe ion toxicity and oxidative stress in cucumber chloroplasts. In addition, salinity caused a significant increase in the saturated fatty acid contents of thylakoid membranes. Put altered unsaturated fatty acid content, thereby alleviating the disintegration of thylakoid grana lamellae and reducing the number of plastoglobuli in thylakoid membranes. BN-PAGE revealed Put up-regulated the expression of ATP synthase, CP47, D1, Qb, and psbA proteins and down-regulated CP24, D2, and LHCII type III in NaCl-stressed thylakoid membranes. qRT-PCR analysis of gene expression was used to compare transcript and protein accumulation among 10 candidate proteins. For five of these proteins, induced transcript accumulation was consistent with the pattern of induced protein accumulation. Our results suggest that Put regulates protein expression at transcriptional and translational levels by increasing endogenous polyamines levels in thylakoid membranes, which may stabilise photosynthetic apparatus under salt stress. PMID:26435404

  16. Removal of aqueous Hg(II) and Cr(VI) using phytic acid doped polyaniline/cellulose acetate composite membrane.

    PubMed

    Li, Renjie; Liu, Lifen; Yang, Fenglin

    2014-09-15

    Conductive composite membrane-phytic acid (PA) doped polyaniline (PANI)/cellulose acetate (CA) (PANI-PA/CA) was prepared in a simple and environmental-friendly method, in which aniline was blended with CA/PA solution and polymerized before the phase conversion. The resultant composite membranes were characterized by SEM, EDX, FTIR-ATR, BET and electrical resistance measurements. When used as adsorbent for Hg(II) and Cr(VI) ions, the prepared composite membrane exhibits excellent adsorption capability. The adsorption of Hg(II) and Cr(VI) follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model, with the maximum adsorption capacity reaching 280.11 and 94.34 mg g(-1), respectively. The heavy metal loaded composite membrane can be regenerated and reused after treatment with acid or alkali solution, making it a promising and practical adsorbent for Hg(II) and Cr(VI) removal. Tests with river water were also carried out, indicating good performance and application.

  17. The Chemical Behavior and Degradation Mitigation Effect of Cerium Oxide Nanoparticles in Perfluorosulfonic Acid Polymer Electrolyte Membranes

    SciTech Connect

    Pearman, Benjamin P; Mohajeri, Nahid; Slattery, Darlene; Hampton, Michael; Seal, Sudipta; Cullen, David A

    2013-01-01

    Perfluorosulfonic acid membranes, the polymer of choice for polymer electrolyte hydrogen fuel cells, are susceptible to degradation due to attacks on polymer chains from radicals. Mitigation of this attack by cerium-based radical scavengers is an approach that has shown promise. In this work, two formulations of single-crystal cerium oxide nanoparticles, with an order of magnitude difference in particle size, are incorporated into said membranes and subjected to proton conductivity measurements and ex-situ durability tests. We found that ceria is reduced to Ce(III) ions in the acidic environment of a heated, humidified membrane which negatively impacts proton conductivity. In liquid and gas Fenton testing, fluoride emission is reduced by an order of magnitude, drastically increasing membrane longevity. Side-product analysis demonstrated that in the liquid Fenton test, the main point of attack are weak polymer end groups, while in the gas Fenton test, there is additional side-chain attack. Both mechanisms are mitigated by the addition of the ceria nanoparticles, whereby the extent of the durability improvement is found to be independent of particle size.

  18. Golgi membrane fission requires the CtBP1-S/BARS-induced activation of lysophosphatidic acid acyltransferase δ.

    PubMed

    Pagliuso, Alessandro; Valente, Carmen; Giordano, Lucia Laura; Filograna, Angela; Li, Guiling; Circolo, Diego; Turacchio, Gabriele; Marzullo, Vincenzo Manuel; Mandrich, Luigi; Zhukovsky, Mikhail A; Formiggini, Fabio; Polishchuk, Roman S; Corda, Daniela; Luini, Alberto

    2016-07-12

    Membrane fission is an essential cellular process by which continuous membranes split into separate parts. We have previously identified CtBP1-S/BARS (BARS) as a key component of a protein complex that is required for fission of several endomembranes, including basolateral post-Golgi transport carriers. Assembly of this complex occurs at the Golgi apparatus, where BARS binds to the phosphoinositide kinase PI4KIIIβ through a 14-3-3γ dimer, as well as to ARF and the PKD and PAK kinases. We now report that, when incorporated into this complex, BARS binds to and activates a trans-Golgi lysophosphatidic acid (LPA) acyltransferase type δ (LPAATδ) that converts LPA into phosphatidic acid (PA); and that this reaction is essential for fission of the carriers. LPA and PA have unique biophysical properties, and their interconversion might facilitate the fission process either directly or indirectly (via recruitment of proteins that bind to PA, including BARS itself).

  19. Conductimetric biosensor for the detection of uric Acid by immobilization uricase on nata de coco membrane-pt electrode.

    PubMed

    Mulyasuryani, Ani; Srihardiastutie, Arie

    2011-01-01

    A conductimetric enzyme biosensor for uric acid detection has been developed. The uricase, as enzyme, is isolated from Candida utilis and immobilized on a nata de coco membrane-Pt electrode. The biosensor demonstrates a linear response to urate over the concentration range 1-6 ppm and has good selectivity properties. The response is affected by the membrane thickness and pH change in the range 7.5-9.5. The response time is three minutes in aqueous solutions and in human serum samples. Application of the biosensor to the determination of uric acid in human serum gave results that compared favourably with those obtained by medical laboratory. The operational stability of the biosensor was not less than three days and the relative error is smaller than 10%.

  20. Golgi membrane fission requires the CtBP1-S/BARS-induced activation of lysophosphatidic acid acyltransferase δ

    PubMed Central

    Pagliuso, Alessandro; Valente, Carmen; Giordano, Lucia Laura; Filograna, Angela; Li, Guiling; Circolo, Diego; Turacchio, Gabriele; Marzullo, Vincenzo Manuel; Mandrich, Luigi; Zhukovsky, Mikhail A.; Formiggini, Fabio; Polishchuk, Roman S.; Corda, Daniela; Luini, Alberto

    2016-01-01

    Membrane fission is an essential cellular process by which continuous membranes split into separate parts. We have previously identified CtBP1-S/BARS (BARS) as a key component of a protein complex that is required for fission of several endomembranes, including basolateral post-Golgi transport carriers. Assembly of this complex occurs at the Golgi apparatus, where BARS binds to the phosphoinositide kinase PI4KIIIβ through a 14-3-3γ dimer, as well as to ARF and the PKD and PAK kinases. We now report that, when incorporated into this complex, BARS binds to and activates a trans-Golgi lysophosphatidic acid (LPA) acyltransferase type δ (LPAATδ) that converts LPA into phosphatidic acid (PA); and that this reaction is essential for fission of the carriers. LPA and PA have unique biophysical properties, and their interconversion might facilitate the fission process either directly or indirectly (via recruitment of proteins that bind to PA, including BARS itself). PMID:27401954

  1. A component of the mitochondrial outer membrane proteome of T. brucei probably contains covalent bound fatty acids.

    PubMed

    Albisetti, Anna; Wiese, Sebastian; Schneider, André; Niemann, Moritz

    2015-08-01

    A subclass of eukaryotic proteins is subject to modification with fatty acids, the most common of which are palmitic and myristic acid. Protein acylation allows association with cellular membranes in the absence of transmembrane domains. Here we examine POMP39, a protein previously described to be present in the outer mitochondrial membrane proteome (POMP) of the protozoan parasite Trypanosoma brucei. POMP39 lacks canonical transmembrane domains, but is likely both myristoylated and palmitoylated on its N-terminus. Interestingly, the protein is also dually localized on the surface of the mitochondrion as well as in the flagellum of both insect-stage and the bloodstream form of the parasites. Upon abolishing of global protein acylation or mutation of the myristoylation site, POMP39 relocates to the cytosol. RNAi-mediated ablation of the protein neither causes a growth phenotype in insect-stage nor bloodstream form trypanosomes.

  2. Golgi membrane fission requires the CtBP1-S/BARS-induced activation of lysophosphatidic acid acyltransferase δ.

    PubMed

    Pagliuso, Alessandro; Valente, Carmen; Giordano, Lucia Laura; Filograna, Angela; Li, Guiling; Circolo, Diego; Turacchio, Gabriele; Marzullo, Vincenzo Manuel; Mandrich, Luigi; Zhukovsky, Mikhail A; Formiggini, Fabio; Polishchuk, Roman S; Corda, Daniela; Luini, Alberto

    2016-01-01

    Membrane fission is an essential cellular process by which continuous membranes split into separate parts. We have previously identified CtBP1-S/BARS (BARS) as a key component of a protein complex that is required for fission of several endomembranes, including basolateral post-Golgi transport carriers. Assembly of this complex occurs at the Golgi apparatus, where BARS binds to the phosphoinositide kinase PI4KIIIβ through a 14-3-3γ dimer, as well as to ARF and the PKD and PAK kinases. We now report that, when incorporated into this complex, BARS binds to and activates a trans-Golgi lysophosphatidic acid (LPA) acyltransferase type δ (LPAATδ) that converts LPA into phosphatidic acid (PA); and that this reaction is essential for fission of the carriers. LPA and PA have unique biophysical properties, and their interconversion might facilitate the fission process either directly or indirectly (via recruitment of proteins that bind to PA, including BARS itself). PMID:27401954

  3. Mass spectrometric detection of cross-linked fatty acids formed during radical-induced lesion of lipid membranes.

    PubMed Central

    Frank, H; Thiel, D; MacLeod, J

    1989-01-01

    A mass spectrometric method is described for the quantitative determination of dimers of polyunsaturated fatty acids (PUFA) formed in the hepatic endoplasmic reticulum of rats upon inhalation of tetrachloromethane. The results show that dimers account for a considerable fraction of microsomal PUFA which disappear during CCl4 metabolism. Cross-linking of the membrane lipids of the endoplasmic reticulum seems to be a significant process with respect to cell toxicity. PMID:2764908

  4. An in vitro study on the antioxidant capacity of usnic acid on human erythrocytes and molecular models of its membrane.

    PubMed

    Suwalsky, M; Jemiola-Rzeminska, M; Astudillo, C; Gallardo, M J; Staforelli, J P; Villena, F; Strzalka, K

    2015-11-01

    Usnic acid (UA) has been associated with chronic diseases through its antioxidant action. Its main target is the cell membrane; however, its effect on that of human erythrocytes has been scarcely investigated. To gain insight into the molecular mechanisms of the interaction between UA and cell membranes human erythrocytes and molecular models of its membrane have been utilized. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. Results by X-ray diffraction showed that UA produced structural perturbations on DMPC and DMPE bilayers. DSC studies have indicated that thermotropic behavior of DMPE was most strongly distorted by UA than DMPC, whereas the latter is mainly affected on the pretransition. Scanning electron (SEM) and defocusing microscopy (DM) showed that UA induced alterations to erythrocytes from the normal discoid shape to echinocytes. These results imply that UA molecules were located in the outer monolayer of the erythrocyte membrane. Results of its antioxidant properties showed that UA neutralized the oxidative capacity of HClO on DMPC and DMPE bilayers; SEM, DM and hemolysis assays demonstrated the protective effect of UA against the deleterious oxidant effects of HClO upon human erythrocytes.

  5. Synthesis of antimicrobial Nisin-phosphorylated soybean protein isolate/poly(L-lactic acid)/ZrO2 membranes.

    PubMed

    Jiang, Suwei; Wang, Hualin; Chu, Chenjiang; Ma, Xingkong; Sun, Min; Jiang, Shaotong

    2015-01-01

    Electrospinning technique was used to fabricate the model drug Nisin loaded phosphorylated soybean protein isolate/poly(l-lactic acid)/zirconium dioxide (Nisin-PSPI/PLLA/ZrO2) nanofibrous membranes. The average diameter of drug carrier PSPI/PLLA/ZrO2 nanofibers increased with the increase of content PSPI and some spindle-shape beads appeared when PSPI content reached 25 wt%. The loading dosage of Nisin caused no significant changes in the size and morphology of nanofibers when Nisin content was below 9 wt%. There existed hydrogen and Zr-O-C bonds among PSPI, PLLA and ZrO2 units, and the crystalline of PLLA matrix decreased owning to the introducing of PSPI and ZrO2 units. Moreover, the water absorption capability and degradation rate of PSPI/PLLA/ZrO2 nanofibrous membranes increased with increasing PSPI content. The antimicrobial activity and release experimental results showed that Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes displayed well controlled release and better antimicrobial activity against Staphylococcus aureus (S. aureus), and the Nisin release from the medicated nanofibers could be described by Fickian diffusion model. The Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes may have potential as a new nanofibrous membrane in drug delivery, food active packaging and wound dressing. PMID:25193100

  6. Synthesis of antimicrobial Nisin-phosphorylated soybean protein isolate/poly(L-lactic acid)/ZrO2 membranes.

    PubMed

    Jiang, Suwei; Wang, Hualin; Chu, Chenjiang; Ma, Xingkong; Sun, Min; Jiang, Shaotong

    2015-01-01

    Electrospinning technique was used to fabricate the model drug Nisin loaded phosphorylated soybean protein isolate/poly(l-lactic acid)/zirconium dioxide (Nisin-PSPI/PLLA/ZrO2) nanofibrous membranes. The average diameter of drug carrier PSPI/PLLA/ZrO2 nanofibers increased with the increase of content PSPI and some spindle-shape beads appeared when PSPI content reached 25 wt%. The loading dosage of Nisin caused no significant changes in the size and morphology of nanofibers when Nisin content was below 9 wt%. There existed hydrogen and Zr-O-C bonds among PSPI, PLLA and ZrO2 units, and the crystalline of PLLA matrix decreased owning to the introducing of PSPI and ZrO2 units. Moreover, the water absorption capability and degradation rate of PSPI/PLLA/ZrO2 nanofibrous membranes increased with increasing PSPI content. The antimicrobial activity and release experimental results showed that Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes displayed well controlled release and better antimicrobial activity against Staphylococcus aureus (S. aureus), and the Nisin release from the medicated nanofibers could be described by Fickian diffusion model. The Nisin-PSPI/PLLA/ZrO2 nanofibrous membranes may have potential as a new nanofibrous membrane in drug delivery, food active packaging and wound dressing.

  7. An in vitro study on the antioxidant capacity of usnic acid on human erythrocytes and molecular models of its membrane.

    PubMed

    Suwalsky, M; Jemiola-Rzeminska, M; Astudillo, C; Gallardo, M J; Staforelli, J P; Villena, F; Strzalka, K

    2015-11-01

    Usnic acid (UA) has been associated with chronic diseases through its antioxidant action. Its main target is the cell membrane; however, its effect on that of human erythrocytes has been scarcely investigated. To gain insight into the molecular mechanisms of the interaction between UA and cell membranes human erythrocytes and molecular models of its membrane have been utilized. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. Results by X-ray diffraction showed that UA produced structural perturbations on DMPC and DMPE bilayers. DSC studies have indicated that thermotropic behavior of DMPE was most strongly distorted by UA than DMPC, whereas the latter is mainly affected on the pretransition. Scanning electron (SEM) and defocusing microscopy (DM) showed that UA induced alterations to erythrocytes from the normal discoid shape to echinocytes. These results imply that UA molecules were located in the outer monolayer of the erythrocyte membrane. Results of its antioxidant properties showed that UA neutralized the oxidative capacity of HClO on DMPC and DMPE bilayers; SEM, DM and hemolysis assays demonstrated the protective effect of UA against the deleterious oxidant effects of HClO upon human erythrocytes. PMID:26299817

  8. The requirement for membrane sialic acid in the stimulation of superoxide production during phagocytosis by human polymorphonuclear leukocytes

    PubMed Central

    1976-01-01

    The effect of desialylation on phagocytosis of latex particles and oxidative metabolism of human polymorphonuclear leukocytes was studied. Removal of 20% total leukocyte sialic acid by bacterial neuraminidase had no effect on phagocytosis of latex particles and phagocytosis- associated activation of hexose monophosphate shunt in human polymorphonuclear leukocytes. In contrast, desialylation prevented the stimulation of superoxide production either by phagocytosis or by concanavalin A. It is concluded that membrane sialic acid is essential for the stimulation of superoxide production by human polymorphonuclear leukocytes. PMID:178821

  9. Improvement of l-lactic acid productivity from sweet sorghum juice by repeated batch fermentation coupled with membrane separation.

    PubMed

    Wang, Yong; Meng, Hongyu; Cai, Di; Wang, Bin; Qin, Peiyong; Wang, Zheng; Tan, Tianwei

    2016-07-01

    In order to efficiently produce l-lactic acid from non-food feedstocks, sweet sorghum juice (SSJ), which is rich of fermentable sugars, was directly used for l-lactic acid fermentation by Lactobacillus rhamnosus LA-04-1. A membrane integrated repeated batch fermentation (MIRB) was developed for productivity improvement. High-cell-density fermentation was achieved with a final cell density (OD620) of 42.3, and the CCR effect was overcomed. When SSJ (6.77gL(-1) glucose, 4.51gL(-1) fructose and 50.46gL(-1) sucrose) was used as carbon source in MIRB process, l-lactic acid productivity was increased significantly from 1.45gL(-1)h(-1) (batch 1) to 17.55gL(-1)h(-1) (batch 6). This process introduces an effective way to produce l-lactic acid from SSJ.

  10. Inhibitory Effect of Long-Chain Fatty Acids on Biogas Production and the Protective Effect of Membrane Bioreactor

    PubMed Central

    Dasa, Kris Triwulan; Westman, Supansa Y.; Cahyanto, Muhammad Nur; Niklasson, Claes

    2016-01-01

    Anaerobic digestion of lipid-containing wastes for biogas production is often hampered by the inhibitory effect of long-chain fatty acids (LCFAs). In this study, the inhibitory effects of LCFAs (palmitic, stearic, and oleic acid) on biogas production as well as the protective effect of a membrane bioreactor (MBR) against LCFAs were examined in thermophilic batch digesters. The results showed that palmitic and oleic acid with concentrations of 3.0 and 4.5 g/L resulted in >50% inhibition on the biogas production, while stearic acid had an even stronger inhibitory effect. The encased cells in the MBR system were able to perform better in the presence of LCFAs. This system exhibited a significantly lower percentage of inhibition than the free cell system, not reaching over 50% at any LCFA concentration tested. PMID:27699172

  11. Inhibitory Effect of Long-Chain Fatty Acids on Biogas Production and the Protective Effect of Membrane Bioreactor

    PubMed Central

    Dasa, Kris Triwulan; Westman, Supansa Y.; Cahyanto, Muhammad Nur; Niklasson, Claes

    2016-01-01

    Anaerobic digestion of lipid-containing wastes for biogas production is often hampered by the inhibitory effect of long-chain fatty acids (LCFAs). In this study, the inhibitory effects of LCFAs (palmitic, stearic, and oleic acid) on biogas production as well as the protective effect of a membrane bioreactor (MBR) against LCFAs were examined in thermophilic batch digesters. The results showed that palmitic and oleic acid with concentrations of 3.0 and 4.5 g/L resulted in >50% inhibition on the biogas production, while stearic acid had an even stronger inhibitory effect. The encased cells in the MBR system were able to perform better in the presence of LCFAs. This system exhibited a significantly lower percentage of inhibition than the free cell system, not reaching over 50% at any LCFA concentration tested.

  12. UV-induced graft polymerization of acrylic acid in the sub-micronchannels of oxidized PET track-etched membrane

    NASA Astrophysics Data System (ADS)

    Korolkov, Ilya V.; Mashentseva, Anastassiya A.; Güven, Olgun; Taltenov, Abzal A.

    2015-12-01

    In this article, we report on functionalization of track-etched membrane based on poly(ethylene terephthalate) (PET TeMs) oxidized by advanced oxidation systems and by grafting of acrylic acid using photochemical initiation technique for the purpose of increasing functionality thus expanding its practical application. Among advanced oxidation processes (H2O2/UV) system had been chosen to introduce maximum concentration of carboxylic acid groups. Benzophenone (BP) photo-initiator was first immobilized on the surfaces of cylindrical pores which were later filled with aq. acrylic acid solution. UV-irradiation from both sides of PET TeMs has led to the formation of grafted poly(acrylic acid) (PAA) chains inside the membrane sub-micronchannels. Effect of oxygen-rich surface of PET TeMs on BP adsorption and subsequent process of photo-induced graft polymerization of acrylic acid (AA) were studied by ESR. The surface of oxidized and AA grafted PET TeMs was characterized by UV-vis, ATR-FTIR, XPS spectroscopies and by SEM.

  13. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells

    PubMed Central

    Komaba, Shigeru; Coluccio, Lynne M.

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  14. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells.

    PubMed

    Komaba, Shigeru; Coluccio, Lynne M

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  15. cis/trans isomerization of unsaturated fatty acids as possible control mechanism of membrane fluidity in Pseudomonas putida P8.

    PubMed

    Loffeld, B; Keweloh, H

    1996-08-01

    Exponentially growing cells of Pseudomonas putida had an increased ratio of saturated to unsaturated fatty acids in response to increased growth temperatures. Resting cells in which fatty acid biosynthesis was stopped reacted to a thermal increase by converting cis-monounsaturated fatty acids to trans isomers. cis/trans Isomerization of up to 60% of the unsaturated fatty acids was also activated by alcohols of different chain length. Their effective concentrations apparently depended on the lipophilic character of the alcohols. Also, a salt shock caused by the addition of NaCl resulted in the production of trans fatty acids. However, cells that were adapted to growth media of high osmolarity synthesized cyclopropane fatty acids instead of trans fatty acids. Activity of cis/trans-isomerase was dependent on the growth phase and was significantly higher during logarithmic growth than during the stationary phase. The results of this study agree with the hypothesis that the isomerization of cis into trans unsaturated fatty acids is an emergency action of cells of P. putida to adapt membrane fluidity to drastic changes of environmental conditions.

  16. Enhancing proton conduction under low humidity by incorporating core-shell polymeric phosphonic acid submicrospheres into sulfonated poly(ether ether ketone) membrane

    NASA Astrophysics Data System (ADS)

    Nie, Lingli; Wang, Jingtao; Xu, Tao; Dong, Hao; Wu, Hong; Jiang, Zhongyi

    2012-09-01

    Polymeric phosphonic acid submicrospheres (PPASs) with carboxylic acid cores and phosphonic acid shells are synthesized by distillation-precipitation polymerization. The structure and composition of PPASs are confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray (EDX). The PPASs are then incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate composite membranes for direct methanol fuel cells (DMFCs). The incorporated PPASs enlarge the ion-channel size of the composite membranes as testified by small-angle X-ray scattering (SAXS), affording significantly enhanced water uptake and water retention. Compared with the membrane containing the polymeric carboxylic acid submicrospheres (PCASs), the PPASs-filled membrane exhibits higher proton conductivity owing to the higher water uptake and water retention of the PPASs and stronger acidity of phosphonic acid. The composite membrane with 15 wt.% PPASs displays the highest proton conductivity of 0.0187 S cm-1 at room temperature and 100% relative humidity (RH). At the RH as low as 20%, this membrane acquires a proton conductivity of 0.0066 S cm-1, 5 times higher than that of the SPEEK control membrane (0.0011 S cm-1) after 90 min testing, at 40 °C.

  17. Penetration depth of surfactant peptide KL4 into membranes is determined by fatty acid saturation.

    PubMed

    Antharam, Vijay C; Elliott, Douglas W; Mills, Frank D; Farver, R Suzanne; Sternin, Edward; Long, Joanna R

    2009-05-20

    KL(4) is a 21-residue functional peptide mimic of lung surfactant protein B, an essential protein for lowering surface tension in the alveoli. Its ability to modify lipid properties and restore lung compliance was investigated with circular dichroism, differential scanning calorimetry, and solid-state NMR spectroscopy. KL(4) binds fluid lamellar phase PC/PG lipid membranes and forms an amphipathic helix that alters lipid organization and acyl chain dynamics. The binding and helicity of KL(4) is dependent on the level of monounsaturation in the fatty acid chains. At physiologic temperatures, KL(4) is more peripheral and dynamic in fluid phase POPC/POPG MLVs but is deeply inserted into fluid phase DPPC/POPG vesicles, resulting in immobilization of the peptide. Substantial increases in the acyl chain order are observed in DPPC/POPG lipid vesicles with increasing levels of KL(4), and POPC/POPG lipid vesicles show small decreases in the acyl chain order parameters on addition of KL(4). Additionally, a clear effect of KL(4) on the orientation of the fluid phase PG headgroups is observed, with similar changes in both lipid environments. Near the phase transition temperature of the DPPC/POPG lipid mixtures, which is just below the physiologic temperature of lung surfactant, KL(4) causes phase separation with the DPPC remaining in a gel phase and the POPG partitioned between gel and fluid phases. The ability of KL(4) to differentially partition into lipid lamellae containing varying levels of monounsaturation and subsequent changes in curvature strain suggest a mechanism for peptide-mediated lipid organization and trafficking within the dynamic lung environment. PMID:19450480

  18. Scalable Fabrication of Electrospun Nanofibrous Membranes Functionalized with Citric Acid for High-Performance Protein Adsorption.

    PubMed

    Fu, Qiuxia; Wang, Xueqin; Si, Yang; Liu, Lifang; Yu, Jianyong; Ding, Bin

    2016-05-11

    Fabricating protein adsorbents with high adsorption capacity and appreciable throughput is extremely important and highly desired for the separation and purification of protein products in the biomedical and pharmaceutical industries, yet still remains a great challenge. Herein, we demonstrate the synthesis of a novel protein adsorbent by in situ functionalizing eletrospun ethylene-vinyl alcohol (EVOH) nanofibrous membranes (NFM) with critic acid (CCA). Taking advantage of the merits of large specific surface area, highly tortuous open-porous structure, abundant active carboxyl groups introduced by CCA, superior chemical stability, and robust mechanical strength, the obtained CCA-grafted EVOH NFM (EVOH-CCA NFM) present an excellent integrated protein (take lysozyme as the model protein) adsorption performance with a high capacity of 284 mg g(-1), short equilibrium time of 6 h, ease of elution, and good reusability. Meanwhile, the adsorption performance of EVOH-CCA NFM can be optimized by regulating buffer pH, ionic strength, and initial concentration of protein solutions. More importantly, a dynamic binding efficiency of 250 mg g(-1) can be achieved driven solely by the gravity of protein solution, which matches well with the demands of the high yield and energy conservation in the actual protein purification process. Furthermore, the resultant EVOH-CCA NFM also possess unique selectivity for positively charged proteins which was confirmed by the method of sodium dodecyl sulfate polyacrylamide gel electrophoresis. Significantly, the successful synthesis of such intriguing and economic EVOH-CCA NFM may provide a promising candidate for the next generation of protein adsorbents for rapid, massive, and cost-effective separation and purification of proteins. PMID:27111287

  19. Boric acid permeation in forward osmosis membrane processes: modeling, experiments, and implications.

    PubMed

    Jin, Xue; Tang, Chuyang Y; Gu, Yangshuo; She, Qianhong; Qi, Saren

    2011-03-15

    Forward osmosis (FO) is attracting increasing interest for its potential applications in desalination. In FO, permeation of contaminants from feed solution into draw solution through the semipermeable membrane can take place simultaneously with water diffusion. Understanding the contaminants transport through and rejection by FO membrane has significant technical implications in the way to separate clean water from the diluted draw solution. In this study, a model was developed to predict boron flux in FO operation. A strong agreement between modeling results and experimental data indicates that the model developed in this study can accurately predict the boron transport through FO membranes. Furthermore, the model can guide the fabrication of improved FO membranes with decreased boron permeability and structural parameter to minimize boron flux. Both theoretical model and experimental results demonstrated that when membrane active layer was facing draw solution, boron flux was substantially greater compared to the other membrane orientation due to more severe internal concentration polarization. In this investigation, for the first time, rejection of contaminants was defined in FO processes. This is critical to compare the membrane performance between different membranes and experimental conditions.

  20. Boric acid permeation in forward osmosis membrane processes: modeling, experiments, and implications.

    PubMed

    Jin, Xue; Tang, Chuyang Y; Gu, Yangshuo; She, Qianhong; Qi, Saren

    2011-03-15

    Forward osmosis (FO) is attracting increasing interest for its potential applications in desalination. In FO, permeation of contaminants from feed solution into draw solution through the semipermeable membrane can take place simultaneously with water diffusion. Understanding the contaminants transport through and rejection by FO membrane has significant technical implications in the way to separate clean water from the diluted draw solution. In this study, a model was developed to predict boron flux in FO operation. A strong agreement between modeling results and experimental data indicates that the model developed in this study can accurately predict the boron transport through FO membranes. Furthermore, the model can guide the fabrication of improved FO membranes with decreased boron permeability and structural parameter to minimize boron flux. Both theoretical model and experimental results demonstrated that when membrane active layer was facing draw solution, boron flux was substantially greater compared to the other membrane orientation due to more severe internal concentration polarization. In this investigation, for the first time, rejection of contaminants was defined in FO processes. This is critical to compare the membrane performance between different membranes and experimental conditions. PMID:21329347

  1. Effects of phytanic acid on the vitamin E status, lipid composition and physical properties of retinal cell membranes: implications for adult Refsum disease.

    PubMed

    Young, S P; Johnson, A W; Muller, D P

    2001-12-01

    Adult Refsum disease is an inherited disorder in which phytanic acid accumulates in tissues and serum. Two hypotheses have been proposed to explain the pathogenesis of this condition. The molecular distortion hypothesis suggests that phytanic acid may alter membrane composition and structure, thereby affecting membrane function(s). The anti-metabolite hypothesis suggests that an accumulation of phytanic acid in membranes may interfere with vitamin E function. These two hypotheses were investigated by studying the effects of modulating phytanic acid and alpha-tocopherol concentrations on the fatty acid composition and certain physical parameters of cultured retinal cells. Results showed that (a) the phospholipid fraction of retinal cells readily incorporated phytanic acid, (b) the incorporation of phytanic acid increased membrane fluidity, (c) there was no competition for uptake between phytanic acid and alpha-tocopherol, and (d) the incorporation of phytanic acid did not increase the susceptibility of membranes to lipid peroxidation in vitro. These results obtained with cultured retinal cells suggest that the molecular distortion hypothesis, but not the anti-metabolite hypothesis, could explain the pathogenesis of adult Refsum disease. In vitro tissue culture models can, however, only approximate to the much more complex situation that occurs in vivo.

  2. 2-Hydroxy Fatty Acid Enantiomers of Gb3 Impact Shiga Toxin Binding and Membrane Organization.

    PubMed

    Schütte, Ole M; Patalag, Lukas J; Weber, Lucas M C; Ries, Annika; Römer, Winfried; Werz, Daniel B; Steinem, Claudia

    2015-06-16

    Shiga toxin subunit B (STxB) binding to its cellular receptor Gb3 leads to the formation of protein-lipid clusters and bending of the membrane. A newly developed synthetic route allowed synthesizing the biologically most relevant Gb3-C24:1 2OH species with both, the natural (Gb3-R) as well as the unnatural (Gb3-S) configuration of the 2OH group. The derivatives bind STxB with identical nanomolar affinity, while the propensity to induce membrane tubules in giant unilamellar vesicles is more pronounced for Gb3-S. Fluorescence and atomic force microscopy images of phase-separated supported membranes revealed differences in the lateral organization of the protein on the membrane. Gb3-R favorably induces large and tightly packed protein clusters, while a lower protein density is found on Gb3-S doped membranes. PMID:26083916

  3. Paramagnetic relaxation enhancement of membrane proteins by incorporation of the metal-chelating unnatural amino acid 2-amino-3-(8-hydroxyquinolin-3-yl) propanoic acid (HQA)

    PubMed Central

    Park, Sang Ho; Wang, Vivian; Radoicic, Jasmina; De Angelis, Anna A.; Berkamp, Sabrina; Opella, Stanley J.

    2014-01-01

    The use of paramagnetic constraints in protein NMR is an active area of research because of the benefits of long-range distance measurements (>10 Å). One of the main issues in successful execution is the incorporation of a paramagnetic metal ion into diamagnetic proteins. The most common metal ion tags are relatively long aliphatic chains attached to the side chain of a selected cysteine residue with a chelating group at the end where it can undergo substantial internal motions, decreasing the accuracy of the method. An attractive alternative approach is to incorporate an unnatural amino acid (UAA) that binds metal ions at a specific site on the protein using the methods of molecular biology. Here we describe the successful incorporation of the unnatural amino acid 2-amino-3-(8-hydroxyquinolin-3-yl) propanoic acid (HQA) into two different membrane proteins by heterologous expression in E. coli. Fluorescence and NMR experiments demonstrate complete replacement of the natural amino acid with HQA and stable metal chelation by the mutated proteins. Evidence of site-specific intra- and inter-molecular PREs by NMR in micelle solutions sets the stage for the use of HQA incorporation in solid-state NMR structure determinations of membrane proteins in phospholipid bilayers. PMID:25430059

  4. Long-chain fatty acid-promoted swelling of mitochondria: further evidence for the protonophoric effect of fatty acids in the inner mitochondrial membrane.

    PubMed

    Schönfeld, P; Wieckowski, M R; Wojtczak, L

    2000-04-01

    Swelling of non-respiring rat liver mitochondria suspended in isotonic potassium acetate at pH 6.5-7.4 in the presence of valinomycin was promoted by long-chain fatty acids, such as myristate, indicating a protonophoric mechanism. This swelling was partly inhibited by inhibitors or substrates of mitochondrial anion carriers. The results show that the fatty acid cycling mechanism responsible for uncoupling of oxidative phosphorylation can also operate in the direction opposite to that originally proposed [Skulachev, V.P. (1991) FEBS Lett. 294, 158-162], i.e. the inwardly directed transfer of the fatty acid anion accompanied by outwardly directed free passage of undissociated fatty acid. They also extend the list of mitochondrial anion carriers, that are involved in this process, over the mono- and tricarboxylate transporters. At pH 8, myristate, but not the synthetic protonophore, p-trifluoromethoxycarbonyl-cyanide phenylhydrazone, induced mitochondrial swelling in both potassium acetate and KCl media, that did not require the presence of valinomycin. This indicates that, at alkaline pH, myristate facilitates permeation of the inner mitochondrial membrane to monovalent cations and, possibly, activates the inner membrane anion channel.

  5. Role of the plasma membrane H+-ATPase in the regulation of organic acid exudation under aluminum toxicity and phosphorus deficiency

    PubMed Central

    Yu, Wenqian; Kan, Qi; Zhang, Jiarong; Zeng, Bingjie; Chen, Qi

    2016-01-01

    Aluminum (Al) toxicity and phosphorus (P) deficiency are 2 major limiting factors for plant growth and crop production in acidic soils. Organic acids exuded from roots have been generally regarded as a major resistance mechanism to Al toxicity and P deficiency. The exudation of organic acids is mediated by membrane-localized OA transporters, such as ALMT (Al-activated malate transporter) and MATE (multidrug and toxic compound extrusion). Beside on up-regulation expression of organic acids transporter gene, transcriptional, translational and post-translational regulation of the plasma membrane H+-ATPase are also involved in organic acid release process under Al toxicity and P deficiency. This mini-review summarizes the current knowledge about this field of study on the role of the plasma membrane H+-ATPase in organic acid exudation under Al toxicity and P deficiency conditions. PMID:26713714

  6. Chronic alcohol consumption augments loss of sialic acid residues and alters erythrocyte membrane charge in type II diabetic patients.

    PubMed

    Degirmenci, Serkan; Akalin, Aysen; Kartkaya, Kazim; Kanbak, Güngör

    2008-01-01

    In this study, the effects of alcohol consumption on erythrocyte membrane properties in type 2 diabetic patients were investigated. Therefore, we measured total and lipid-bound sialic acid (LSA) levels, sialidase activities, and erythrocyte membrane negative charge. Three groups, including control group (n = 20), alcohol-consuming diabetic patients group (n = 14), and diabetic patients without alcohol consumption group (n = 42), were created. Plasma total sialic acid (TSA) levels of the alcohol-consuming diabetic group were elevated as compared to the healthy control and diabetic group (p < 0.001 and p < 0.01, respectively). TSA levels of the diabetic group were significantly elevated as compared to the healthy control group (p > 0.001). Plasma LSA levels of the alcohol-consuming diabetic group were higher than that in the healthy control and diabetic group (p < 0.05 and p < 0.05, respectively). LSA levels of the diabetic group were found to be high as compared to the healthy control group (p < 0.05). Plasma sialidase activities of the alcohol-consuming diabetic group and diabetic group were significantly elevated as compared to the healthy control group (p < 0.05 and p < 0.05, respectively). Sialidase activities of the alcohol-consuming diabetic group were elevated as compared to the diabetic group, but this was not statistically significant (p > 0.05). Erythrocyte membrane negativity levels of the alcohol-consuming diabetic group and diabetic group were significantly decreased (p < 0.001 and p < 0.001, respectively) as compared to the healthy control group. Erythrocyte membrane negativity levels of the alcohol-consuming diabetic group were decreased as compared to the diabetic group, but this was not statistically significant (p > 0.05). In conclusion, our results indicate that chronic alcohol consumption may augment membrane alterations in type 2 diabetic patients.

  7. Identification and biophysical characterization of a very-long-chain-fatty-acid-substituted phosphatidylinositol in yeast subcellular membranes

    PubMed Central

    2004-01-01

    Morphological analysis of a conditional yeast mutant in acetyl-CoA carboxylase acc1ts/mtr7, the rate-limiting enzyme of fatty acid synthesis, suggested that the synthesis of C26 VLCFAs (very-long-chain fatty acids) is important for maintaining the structure and function of the nuclear membrane. To characterize this C26-dependent pathway in more detail, we have now examined cells that are blocked in pathways that require C26. In yeast, ceramide synthesis and remodelling of GPI (glycosylphosphatidylinositol)-anchors are two pathways that incorporate C26 into lipids. Conditional mutants blocked in either ceramide synthesis or the synthesis of GPI anchors do not display the characteristic alterations of the nuclear envelope observed in acc1ts, indicating that the synthesis of another C26-containing lipid may be affected in acc1ts mutant cells. Lipid analysis of isolated nuclear membranes revealed the presence of a novel C26-substituted PI (phosphatidylinositol). This C26-PI accounts for approx. 1% of all the PI species, and is present in both the nuclear and the plasma membrane. Remarkably, this C26-PI is the only C26-containing glycerophospholipid that is detectable in wild-type yeast, and the C26-substitution is highly specific for the sn-1 position of the glycerol backbone. To characterize the biophysical properties of this lipid, it was chemically synthesized. In contrast to PIs with normal long-chain fatty acids (C16 or C18), the C26-PI greatly reduced the bilayer to hexagonal phase transition of liposomes composed of 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE). The biophysical properties of this lipid are thus consistent with a possible role in stabilizing highly curved membrane domains. PMID:15270698

  8. A novel tridentate bis(phosphinic acid)phosphine oxide based europium(III)-selective Nafion membrane luminescent sensor.

    PubMed

    Sainz-Gonzalo, F J; Popovici, C; Casimiro, M; Raya-Barón, A; López-Ortiz, F; Fernández, I; Fernández-Sánchez, J F; Fernández-Gutiérrez, A

    2013-10-21

    A new europium(III) membrane luminescent sensor based on a new tridentate bis(phosphinic acid)phosphine oxide (3) system has been developed. The synthesis of this new ligand is described and its full characterization by NMR, IR and elemental analyses is provided. The luminescent complex formed between europium(III) chloride and ligand 3 was evaluated in solution, observing that its spectroscopic and chemical characteristics are excellent for measuring in polymer inclusion membranes. Included in a Nafion membrane, all the parameters (ligand and ionic additives) that can affect the sensitivity and selectivity of the sensing membrane as well as the instrumental conditions were carefully optimized. The best luminescence signal (λexc = 229.06 nm and λem = 616.02 nm) was exhibited by the sensing film having a Nafion : ligand composition of 262.3 : 0.6 mg mL(-1). The membrane sensor showed a short response time (t95 = 5.0 ± 0.2 min) and an optimum working pH of 5.0 (25 mM acetate buffer solution). The membrane sensor manifested a good selectivity toward europium(III) ions with respect to other trivalent metals (iron, chromium and aluminium) and lanthanide(III) ions (lanthanum, samarium, terbium and ytterbium), although a small positive interference of terbium(III) ions was observed. It provided a linear range from 1.9 × 10(-8) to 5.0 × 10(-6) M with a very low detection limit (5.8 × 10(-9) M) and sensitivity (8.57 × 10(-7) a.u. per M). The applicability of this sensing film has been demonstrated by analyzing different kinds of spiked water samples obtaining recovery percentages of 95-97%.

  9. Facilitated transporters mediate net efflux of amino acids to the fetus across the basal membrane of the placental syncytiotrophoblast.

    PubMed

    Cleal, J K; Glazier, J D; Ntani, G; Crozier, S R; Day, P E; Harvey, N C; Robinson, S M; Cooper, C; Godfrey, K M; Hanson, M A; Lewis, R M

    2011-02-15

    Fetal growth depends on placental transfer of amino acids from maternal to fetal blood. The mechanisms of net amino acid efflux across the basal membrane (BM) of the placental syncytiotrophoblast to the fetus, although vital for amino acid transport, are poorly understood. We examined the hypothesis that facilitated diffusion by the amino acid transporters TAT1, LAT3 and LAT4 plays an important role in this process, with possible effects on fetal growth. Amino acid transfer was measured in isolated perfused human placental cotyledons (n = 5 per experiment) using techniques which distinguish between different transport processes. Placental TAT1, LAT3 and LAT4 proteins were measured, and mRNA expression levels (measured using real-time quantitative-PCR) were related to fetal and neonatal anthropometry and dual-energy X-ray absorptiometry measurements of neonatal lean mass in 102 Southampton Women's Survey (SWS) infants. Under conditions preventing transport by amino acid exchangers, all amino acids appearing in the fetal circulation were substrates of TAT1, LAT3 or LAT4. Western blots demonstrated the presence of TAT1, LAT3 and LAT4 in placental BM preparations. Placental TAT1 and LAT3 mRNA expression were positively associated with measures of fetal growth in SWS infants (P < 0.05). We provide evidence that the efflux transporters TAT1, LAT3 and LAT4 are present in the human placental BM, and may play an important role in the net efflux of amino acids to the fetus. Unlike other transporters they can increase fetal amino acid concentrations. Consistent with a role in placental amino acid transfer capacity and fetal growth TAT1 and LAT3 mRNA expression showed positive associations with infant size at birth.

  10. Structure-based drug design targeting the cell membrane receptor GPBAR1: exploiting the bile acid scaffold towards selective agonism

    NASA Astrophysics Data System (ADS)

    di Leva, Francesco Saverio; Festa, Carmen; Renga, Barbara; Sepe, Valentina; Novellino, Ettore; Fiorucci, Stefano; Zampella, Angela; Limongelli, Vittorio

    2015-11-01

    Bile acids can regulate nutrient metabolism through the activation of the cell membrane receptor GPBAR1 and the nuclear receptor FXR. Developing an exogenous control over these receptors represents an attractive strategy for the treatment of enterohepatic and metabolic disorders. A number of dual GPBAR1/FXR agonists are known, however their therapeutic use is limited by multiple unwanted effects due to activation of the diverse downstream signals controlled by the two receptors. On the other hand, designing selective GPBAR1 and FXR agonists is challenging since the two proteins share similar structural requisites for ligand binding. Here, taking advantage of our knowledge of the two targets, we have identified through a rational drug design study a series of amine lithocholic acid derivatives as selective GPBAR1 agonists. The presence of the 3α-NH2 group on the steroidal scaffold is responsible for the selectivity over FXR unveiling unprecedented structural insights into bile acid receptors activity modulation.

  11. Structure-based drug design targeting the cell membrane receptor GPBAR1: exploiting the bile acid scaffold towards selective agonism

    PubMed Central

    Di Leva, Francesco Saverio; Festa, Carmen; Renga, Barbara; Sepe, Valentina; Novellino, Ettore; Fiorucci, Stefano; Zampella, Angela; Limongelli, Vittorio

    2015-01-01

    Bile acids can regulate nutrient metabolism through the activation of the cell membrane receptor GPBAR1 and the nuclear receptor FXR. Developing an exogenous control over these receptors represents an attractive strategy for the treatment of enterohepatic and metabolic disorders. A number of dual GPBAR1/FXR agonists are known, however their therapeutic use is limited by multiple unwanted effects due to activation of the diverse downstream signals controlled by the two receptors. On the other hand, designing selective GPBAR1 and FXR agonists is challenging since the two proteins share similar structural requisites for ligand binding. Here, taking advantage of our knowledge of the two targets, we have identified through a rational drug design study a series of amine lithocholic acid derivatives as selective GPBAR1 agonists. The presence of the 3α-NH2 group on the steroidal scaffold is responsible for the selectivity over FXR unveiling unprecedented structural insights into bile acid receptors activity modulation. PMID:26567894

  12. Derivatives of the cationic plant alkaloids berberine and palmatine amplify protonophorous activity of fatty acids in model membranes and mitochondria.

    PubMed

    Pustovidko, Antonina V; Rokitskaya, Tatiana I; Severina, Inna I; Simonyan, Ruben A; Trendeleva, Tatiana A; Lyamzaev, Konstantin G; Antonenko, Yuri N; Rogov, Anton G; Zvyagilskaya, Renata A; Skulachev, Vladimir P; Chernyak, Boris V

    2013-09-01

    Previously it has been shown by our group that berberine and palmatine, penetrating cations of plant origin, when conjugated with plastoquinone (SkQBerb and SkQPalm), can accumulate in isolated mitochondria or in mitochondria of living cells and effectively protect them from oxidative damage. In the present work, we demonstrate that SkQBerb, SkQPalm, and their analogs lacking the plastoquinone moiety (C10Berb and C10Palm) operate as mitochondria-targeted compounds facilitating protonophorous effect of free fatty acids. These compounds induce proton transport mediated by small concentrations of added fatty acids both in planar and liposomal model lipid membranes. In mitochondria, such an effect can be carried out by endogenous fatty acids and the adenine nucleotide translocase.

  13. Coupling acidic organelles with the ER through Ca²⁺ microdomains at membrane contact sites.

    PubMed

    Penny, Christopher J; Kilpatrick, Bethan S; Eden, Emily R; Patel, Sandip

    2015-10-01

    Acidic organelles such as lysosomes serve as non-canonical Ca(2+) stores. The Ca(2+) mobilising messenger NAADP is thought to trigger local Ca(2+) release from such stores. These events are then amplified by Ca(2+) channels on canonical ER Ca(2+) stores to generate physiologically relevant global Ca(2+) signals. Coupling likely occurs at microdomains formed at membrane contact sites between acidic organelles and the ER. Molecular analyses and computational modelling suggest heterogeneity in the composition of these contacts and predicted Ca(2+) microdomain behaviour. Conversely, acidic organelles might also locally amplify and temper ER-evoked Ca(2+) signals. Ca(2+) microdomains between distinct Ca(2+) stores are thus likely to be integral to the genesis of complex Ca(2+) signals. PMID:25866010

  14. Evaluation of Zosteric Acid for Mitigating Biofilm Formation of Pseudomonas putida Isolated from a Membrane Bioreactor System

    PubMed Central

    Polo, Andrea; Foladori, Paola; Ponti, Benedetta; Bettinetti, Roberta; Gambino, Michela; Villa, Federica; Cappitelli, Francesca

    2014-01-01

    This study provides data to define an efficient biocide-free strategy based on zosteric acid to counteract biofilm formation on the membranes of submerged bioreactor system plants. 16S rRNA gene phylogenetic analysis showed that gammaproteobacteria was the prevalent taxa on fouled membranes of an Italian wastewater plant. Pseudomonas was the prevalent genus among the cultivable membrane-fouler bacteria and Pseudomonas putida was selected as the target microorganism to test the efficacy of the antifoulant. Zosteric acid was not a source of carbon and energy for P. putida cells and, at 200 mg/L, it caused a reduction of bacterial coverage by 80%. Biofilm experiments confirmed the compound caused a significant decrease in biomass (−97%) and thickness (−50%), and it induced a migration activity of the peritrichous flagellated P. putida over the polycarbonate surface not amenable to a biofilm phenotype. The low octanol-water partitioning coefficient and the high water solubility suggested a low bioaccumulation potential and the water compartment as its main environmental recipient and capacitor. Preliminary ecotoxicological tests did not highlight direct toxicity effects toward Daphnia magna. For green algae Pseudokirchneriella subcapitata an effect was observed at concentrations above 100 mg/L with a significant growth of protozoa that may be connected to a concurrent algal growth inhibition. PMID:24879523

  15. Kinase Associated-1 Domains Drive MARK/PAR1 Kinases to Membrane Targets by Binding Acidic Phospholipids

    SciTech Connect

    Moravcevic, Katarina; Mendrola, Jeannine M.; Schmitz, Karl R.; Wang, Yu-Hsiu; Slochower, David; Janmey, Paul A.; Lemmon, Mark A.

    2011-09-28

    Phospholipid-binding modules such as PH, C1, and C2 domains play crucial roles in location-dependent regulation of many protein kinases. Here, we identify the KA1 domain (kinase associated-1 domain), found at the C terminus of yeast septin-associated kinases (Kcc4p, Gin4p, and Hsl1p) and human MARK/PAR1 kinases, as a membrane association domain that binds acidic phospholipids. Membrane localization of isolated KA1 domains depends on phosphatidylserine. Using X-ray crystallography, we identified a structurally conserved binding site for anionic phospholipids in KA1 domains from Kcc4p and MARK1. Mutating this site impairs membrane association of both KA1 domains and intact proteins and reveals the importance of phosphatidylserine for bud neck localization of yeast Kcc4p. Our data suggest that KA1 domains contribute to coincidence detection, allowing kinases to bind other regulators (such as septins) only at the membrane surface. These findings have important implications for understanding MARK/PAR1 kinases, which are implicated in Alzheimer's disease, cancer, and autism.

  16. [Effects of exogenous salicylic acid on membrane lipid peroxidation and photosynthetic characteristics of Cucumis sativus seedlings under drought stress].

    PubMed

    Hao, Jing-Hong; Yi, Yang; Shang, Qing-Mao; Dong, Chun-Juan; Zhang, Zhi-Gang

    2012-03-01

    To approach the related mechanisms of exogenous salicylic acid (SA) in improving plant drought-resistance, this paper studied the effects of applying exogenous SA to the rhizosphere on the plant growth, membrane lipid peroxidation, proline accumulation, water use efficiency, net photosynthetic rate (Pn), and chlorophyll fluorescence parameters of cucumber (Cucumis sativus) seedlings under drought stresses (60% and 50% of saturated water capacity). Applying SA relieved the inhibitory effects of drought stress on plant growth, Pn, and water use efficiency, decreased membrane lipid peroxidation, and promoted proline accumulation. Meanwhile, the SA decreased the decrements of the maximum photochemical efficiency of PS II, actual photochemical efficiency of PS II, potential activity of PS II, effective photochemical efficiency of PS II, and photochemical quenching coefficient under drought stress significantly, and limited the increase of non-photochemical quenching coefficient. All the results suggested that applying exogenous SA could alleviate the oxidation damage of cell membrane resulted from the drought-caused membrane lipid peroxidation, improve the Pn by increasing PS II activity to benefit water utilization, enhance the regulation capability of osmosis to decrease water loss and increase water use efficiency, and thereby, improve the plant drought-resistance.

  17. Towards Acid-Tolerated Ethanol Dehydration: Chitosan-Based Mixed Matrix Membranes Containing Cyano-Bridged Coordination Polymer Nanoparticles.

    PubMed

    Wu, C-W; Kang, Chao-Hsiang; Lin, Yi-Feng; Tung, Kuo-Lun; Deng, Yu-Heng; Ahamad, Tansir; Alshehri, Saad M; Suzuki, Norihiro; Yamauchi, Yusuke

    2016-04-01

    Prussian blue (PB) nanoparticles, one of many cyano-bridged coordination polymers, are successfully incorporated into chitosan (CS) polymer to prepare PB/CS mixed matrix membranes (MMMs). The PB nanoparticles are uniformly distributed in the MMMs without the collapse of the original PB structure. As-prepared PB/CS MMMs are used for ethanol dehydration at 25 °C in the pervaporation process. The effect of loading PB in CS matrix on pervaporation performance is carefully investigated. The PB/CS membrane with 30 wt% PB loading shows the best performance with a permeate flux of 614 g. m-2 . h-1 and a separation factor of 1472. The pervaporation using our PB/CS membranes exhibits outstanding performance in comparison with the previously reported CS-based membranes and MMMs. Furthermore, the addition of PB allows PB/CS MMMs to be tolerant of acidic environment. The present work demonstrates good pervaporation performance of PB/CS MMMs for the separation of an ethanol/water (90:10 in wt%) solution. Our new system provides an opportunity for dehydration of bioethanol in the future. PMID:27451778

  18. Towards Acid-Tolerated Ethanol Dehydration: Chitosan-Based Mixed Matrix Membranes Containing Cyano-Bridged Coordination Polymer Nanoparticles.

    PubMed

    Wu, C-W; Kang, Chao-Hsiang; Lin, Yi-Feng; Tung, Kuo-Lun; Deng, Yu-Heng; Ahamad, Tansir; Alshehri, Saad M; Suzuki, Norihiro; Yamauchi, Yusuke

    2016-04-01

    Prussian blue (PB) nanoparticles, one of many cyano-bridged coordination polymers, are successfully incorporated into chitosan (CS) polymer to prepare PB/CS mixed matrix membranes (MMMs). The PB nanoparticles are uniformly distributed in the MMMs without the collapse of the original PB structure. As-prepared PB/CS MMMs are used for ethanol dehydration at 25 °C in the pervaporation process. The effect of loading PB in CS matrix on pervaporation performance is carefully investigated. The PB/CS membrane with 30 wt% PB loading shows the best performance with a permeate flux of 614 g. m-2 . h-1 and a separation factor of 1472. The pervaporation using our PB/CS membranes exhibits outstanding performance in comparison with the previously reported CS-based membranes and MMMs. Furthermore, the addition of PB allows PB/CS MMMs to be tolerant of acidic environment. The present work demonstrates good pervaporation performance of PB/CS MMMs for the separation of an ethanol/water (90:10 in wt%) solution. Our new system provides an opportunity for dehydration of bioethanol in the future.

  19. Increased mucociliary differentiation and aquaporins formation of respiratory epithelial cells on retinoic acid-loaded hyaluronan-derivative membranes.

    PubMed

    Huang, Tsung-Wei; Chan, Yen-Hui; Su, Huang-Wei; Chou, Ya-Shuan; Young, Tai-Horng

    2013-06-01

    While playing a major role in maintaining the mucociliary phenotype of respiratory epithelial cells (RECs), retinoids are critical determinants of their normal function. However, despite being a powerful biological agent, retinoic acid (RA) is generally not used in regenerative medicine due to its scarce bioavailability via conventional administration. Therefore, the ability to incorporate RA into biomaterials allows for a combination of the biological effects of RA and biomaterials in influencing cellular behavior. This study attempts to develop RA-loaded hyaluronan-derivative membrane (RA-HAm) and investigates how this membrane affects the mucociliary differentiation and aquaporins (AQP) formation of RECs. In a simulated in vitro culture condition, the RA release from membranes is maintained for 7days. On the seventh day, the cumulative release rate of RA from supportive biomaterials is ~87% under detect limitation. RECs cultured on RA-HAm reveal numerous mature ciliated cells and microvilli compared to aggregated cilia-like structures on hyaluronan-derivative membrane (HAm). Moreover, the expression levels of MUC5AC and AQP on RA-HAm are higher than those on HAm. The proposed model elucidates the release of hydrophobic RA from hyaluronan-derivative biomaterials. We believe that RA-loaded hyaluronan biomaterials are highly promising biomaterials for use in sinonasal surgery and tissue engineering of the respiratory system.

  20. Metabolic rate and membrane fatty acid composition in birds: a comparison between long-living parrots and short-living fowl.

    PubMed

    Montgomery, Magdalene K; Hulbert, A J; Buttemer, William A

    2012-01-01

    Both basal metabolic rate (BMR) and maximum lifespan potential (MLSP) vary with body size in mammals and birds and it has been suggested that these are mediated through size-related variation in membrane fatty acid composition. Whereas the physical properties of membrane fatty acids affect the activity of membrane proteins and, indirectly, an animal's BMR, it is the susceptibility of those fatty acids to peroxidation which influence MLSP. Although there is a correlation between body size and MLSP, there is considerable MLSP variation independent of body size. For example, among bird families, Galliformes (fowl) are relatively short-living and Psittaciformes (parrots) are unusually long-living, with some parrot species reaching maximum lifespans of more than 100 years. We determined BMR and tissue phospholipid fatty acid composition in seven tissues from three species of parrots with an average MLSP of 27 years and from two species of quails with an average MLSP of 5.5 years. We also characterised mitochondrial phospholipids in two of these tissues. Neither BMR nor membrane susceptibility to peroxidation corresponded with differences in MLSP among the birds we measured. We did find that (1) all birds had lower n-3 polyunsaturated fatty acid content in mitochondrial membranes compared to those of the corresponding tissue, and that (2) irrespective of reliance on flight for locomotion, both pectoral and leg muscle had an almost identical membrane fatty acid composition in all birds.

  1. ADSORPTION AND MEMBRANE SEPARATION MEASUREMENTS WITH MIXTURES OF ETHANOL, ACETIC ACID, AND WATER

    EPA Science Inventory

    Biomass fermentation produces ethanol and other renewable biofuels. Pervaporation using hydrophobic membranes is potentially a cost-effective means of removing biofuels from fermentation broths for small- to medium-scale applications. Silicalite-filled polydimethylsiloxane (PDMS)...

  2. Increased ubiquitination and reduced plasma membrane trafficking of placental amino acid transporter SNAT-2 in human IUGR.

    PubMed

    Chen, Yi-Yung; Rosario, Fredrick J; Shehab, Majida Abu; Powell, Theresa L; Gupta, Madhulika B; Jansson, Thomas

    2015-12-01

    Placental amino acid transport is decreased in intrauterine growth restriction (IUGR); however, the underlying mechanisms remain largely unknown. We have shown that mechanistic target of rapamycin (mTOR) signalling regulates system A amino acid transport by modulating the ubiquitination and plasma membrane trafficking of sodium-coupled neutral amino acid transporter 2 (SNAT-2) in cultured primary human trophoblast cells. We hypothesize that IUGR is associated with (1) inhibition of placental mTORC1 and mTORC2 signalling pathways, (2) increased amino acid transporter ubiquitination in placental homogenates and (3) decreased protein expression of SNAT-2 in the syncytiotrophoblast microvillous plasma membrane (MVM). To test this hypothesis, we collected placental tissue and isolated MVM from women with pregnancies complicated by IUGR (n=25) and gestational age-matched women with appropriately grown control infants (n=19, birth weights between the twenty-fifth to seventy-fifth percentiles). The activity of mTORC1 and mTORC2 was decreased whereas the protein expression of the ubiquitin ligase NEDD4-2 (neural precursor cell expressed developmentally down-regulated protein 4-2; +72%, P<0.0001) and the ubiquitination of SNAT-2 (+180%, P<0.05) were increased in homogenates of IUGR placentas. Furthermore, IUGR was associated with decreased system A amino acid transport activity (-72%, P<0.0001) and SNAT-1 (-42%, P<0.05) and SNAT-2 (-31%, P<0.05) protein expression in MVM. In summary, these findings are consistent with the possibility that decreased placental mTOR activity causes down-regulation of placental system A activity by shifting SNAT-2 trafficking towards proteasomal degradation, thereby contributing to decreased fetal amino acid availability and restricted fetal growth in IUGR. PMID:26374858

  3. Metabolic depression during aestivation does not involve remodelling of membrane fatty acids in two Australian frogs.

    PubMed

    Berner, Nancy J; Else, P L; Hulbert, A J; Mantle, B L; Cramp, R L; Franklin, C E

    2009-10-01

    Changes in membrane lipid composition (membrane remodelling) have been associated with metabolic depression in some aestivating snails but has not been studied in aestivating frogs. This study examined the membrane phospholipid composition of two Australian aestivating frog species Cyclorana alboguttata and Cyclorana australis. The results showed no major membrane remodelling of tissue in either frog species, or in mitochondria of C. alboguttata due to aestivation. Mitochondrial membrane remodelling was not investigated in C. australis. Where investigated in C. alboguttata, total protein and phospholipid content, and citrate synthase (CS) and cytochrome c oxidase (CCO) activities in tissues and mitochondria mostly did not change with aestivation in liver. In skeletal muscle, however, CS and CCO activities, mitochondrial and tissue phospholipids, and mitochondrial protein decreased with aestivation. These decreases in muscle indicate that skeletal muscle mitochondrial content may decrease during aestivation. Na(+)K(+)ATPase activity of both frog species showed no effect of aestivation. In C. alboguttata different fat diets had a major effect on both tissue and mitochondrial phospholipid composition indicating an ability to remodel membrane composition that is not utilised in aestivation. Therefore, changes in lipid composition associated with some aestivating snails do not occur during aestivation in these Australian frogs.

  4. Dietary Phenolic Acids Act as Effective Antioxidants in Membrane Models and in Cultured Cells, Exhibiting Proapoptotic Effects in Leukaemia Cells

    PubMed Central

    Zambonin, Laura; Caliceti, Cristiana; Vieceli Dalla Sega, Francesco; Fiorentini, Diana; Hrelia, Silvana; Landi, Laura; Prata, Cecilia

    2012-01-01

    Caffeic, syringic, and protocatechuic acids are phenolic acids derived directly from food intake or come from the gut metabolism of polyphenols. In this study, the antioxidant activity of these compounds was at first evaluated in membrane models, where caffeic acid behaved as a very effective chain-breaking antioxidant, whereas syringic and protocatechuic acids were only retardants of lipid peroxidation. However, all three compounds acted as good scavengers of reactive species in cultured cells subjected to exogenous oxidative stress produced by low level of H2O2. Many tumour cells are characterised by increased ROS levels compared with their noncancerous counterparts. Therefore, we investigated whether phenolic acids, at low concentrations, comparable to those present in human plasma, were able to decrease basal reactive species. Results show that phenolic acids reduced ROS in a leukaemia cell line (HEL), whereas no effect was observed in normal cells, such as HUVEC. The compounds exhibited no toxicity to normal cells while they decreased proliferation in leukaemia cells, inducing apoptosis. In the debate on optimal ROS-manipulating strategies in cancer therapy, our work in leukaemia cells supports the antioxidant ROS-depleting approach. PMID:22792417

  5. Effects of alpha-linolenic acid vs. docosahexaenoic acid supply on the distribution of fatty acids among the rat cardiac subcellular membranes after a short- or long-term dietary exposure

    PubMed Central

    Brochot, Amandine; Guinot, Marine; Auchere, Daniel; Macaire, Jean-Paul; Weill, Pierre; Grynberg, Alain; Rousseau-Ralliard, Delphine

    2009-01-01

    Background Previous work showed that the functional cardiac effect of dietary alpha-linolenic acid (ALA) in rats requires a long feeding period (6 months), although a docosahexaenoic (DHA) acid-supply affects cardiac adrenergic response after 2 months. However, the total cardiac membrane n-3 polyunsaturated fatty acid (PUFA) composition remained unchanged after 2 months. This delay could be due to a specific reorganization of the different subcellular membrane PUFA profiles. This study was designed to investigate the evolution between 2 and 6 months of diet duration of the fatty acid profile in sarcolemmal (SL), mitochondrial (MI), nuclear (NU) and sarcoplasmic reticulum (SR) membrane fractions. Methods Male Wistar rats were randomly assigned to 3 dietary groups (n = 10/diet/period), either n-3 PUFA-free diet (CTL), or ALA or DHA-rich diets. After 2 or 6 months, the subcellular cardiac membrane fractions were separated by differential centrifugations and sucrose gradients. Each membrane profile was analysed by gas chromatography (GC) after lipid extraction. Results As expected the n-3 PUFA-rich diets incorporated n-3 PUFA instead of n-6 PUFA in all the subcellular fractions, which also exhibited individual specificities. The diet duration increased SFA and decreased PUFA in SL, whereas NU remained constant. The SR and MI enriched in n-3 PUFA exhibited a decreased DHA level with ageing in the DHA and CTL groups. Conversely, the n-3 PUFA level remained unchanged in the ALA group, due to a significant increase in docosapentaenoic acid (DPA). N-3 PUFA rich diets lead to a better PUFA profile in all the fractions and significantly prevent the profile modifications induced by ageing. Conclusion With the ALA diet the n-3 PUFA content, particularly in SR and SL kept increasing between 2 and 6 months, which may partly account for the delay to achieve the modification of adrenergic response. PMID:19320987

  6. A DFT Study on the Dissociation Property of Sulfonic Acids with Different Neighboring Pendants in Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    Zhao, Yuan-yuan; Tsuchida, Eiji; Choe, Yoong-Kee; Ikeshoji, Tamio; Ohira, Akihiro

    The proton dissociation property of four model compounds of polymer electrolyte membranes, M1-M4, has been studied based on density functional theory. These four model compounds have the same proton donor group, sulfonic acid, while differ by types of neighboring pendants, non-fluorinated and fluorinated. We find that the protons in the fluorinated model compounds can be dissociated when hydrated by 3 water molecules, comparable to Nafion, while for those non-fluorinated compounds, the protons can be dissociated only hydrated by 4 water molecules. The results indicate that the neighboring pendants have a significant effect on the proton dissociation property of the model compounds. The electron-withdrawing group involved in the neighboring pendants can improve the proton dissociation property of the compounds, which would be meaningful for finding a novel polymer electrolyte membrane with good conductivity.

  7. Development of a submerged anaerobic membrane bioreactor for concurrent extraction of volatile fatty acids and biohydrogen production.

    PubMed

    Trad, Zaineb; Akimbomi, Julius; Vial, Christophe; Larroche, Christian; Taherzadeh, Mohammad J; Fontaine, Jean-Pierre

    2015-11-01

    The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH2) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10(4)Pa, was required to achieve a 3Lh(-1)m(-2) critical flux. During fermentation, BioH2 production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH2 production and the recovery of VFAs as platform molecules.

  8. Development of a submerged anaerobic membrane bioreactor for concurrent extraction of volatile fatty acids and biohydrogen production.

    PubMed

    Trad, Zaineb; Akimbomi, Julius; Vial, Christophe; Larroche, Christian; Taherzadeh, Mohammad J; Fontaine, Jean-Pierre

    2015-11-01

    The aim of this work was to study an externally-submerged membrane bioreactor for the cyclic extraction of volatile fatty acids (VFAs) during anaerobic fermentation, combining the advantages of submerged and external technologies for enhancing biohydrogen (BioH2) production from agrowaste. Mixing and transmembrane pressure (TMP) across a hollow fiber membrane placed in a recirculation loop coupled to a stirred tank were investigated, so that the loop did not significantly modify the hydrodynamic properties in the tank. The fouling mechanism, due to cake layer formation, was reversible. A cleaning procedure based on gas scouring and backwashing with the substrate was defined. Low TMP, 10(4)Pa, was required to achieve a 3Lh(-1)m(-2) critical flux. During fermentation, BioH2 production was shown to restart after removing VFAs with the permeate, so as to enhance simultaneously BioH2 production and the recovery of VFAs as platform molecules. PMID:26253913

  9. Isolation and characterization of an amino acid-selective channel protein present in the chloroplastic outer envelope membrane

    PubMed Central

    Pohlmeyer, Kai; Soll, Jürgen; Steinkamp, Thomas; Hinnah, Silke; Wagner, Richard

    1997-01-01

    The reconstituted pea chloroplastic outer envelope protein of 16 kDa (OEP16) forms a slightly cation-selective, high-conductance channel with a conductance of Λ = 1,2 nS (in 1 M KCl). The open probability of OEP16 channel is highest at 0 mV (Popen = 0.8), decreasing exponentially with higher potentials. Transport studies using reconstituted recombinant OEP16 protein show that the OEP16 channel is selective for amino acids but excludes triosephosphates or uncharged sugars. Crosslinking indicates that OEP16 forms a homodimer in the membrane. According to its primary sequence and predicted secondary structure, OEP16 shows neither sequence nor structural homologies to classical porins. The results indicate that the intermembrane space between the two envelope membranes might not be as freely accessible as previously thought. PMID:9256512

  10. Effect of Ammonium- and Phosphonium-Based Ionic Liquids on the Separation of Lactic Acid by Supported Ionic Liquid Membranes (SILMs)

    PubMed Central

    Matsumoto, Michiaki; Panigrahi, Abhishek; Murakami, Yuuki; Kondo, Kazuo

    2011-01-01

    Biodegradable polymers have attracted much attention from an environmental point of view. Optically pure lactic acid that can be prepared by fermentation is one of the important raw materials for biodegradable polymer. The separation and purification of lactic acid from the fermentation broth are the major portions of the production costs. We proposed the application of supported ionic liquid membranes to recovering lactic acid. In this paper, the effect of ionic liquids, such as Aliquat 336, CYPHOS IL-101, CYPHOS IL-102, CYPHOS IL-104, CYPHOS IL-109 and CYPHOS IL-111 on the lactic acid permeation have been studied. Aliquat 336, CYPHOS IL-101 and CYPHOS IL-102 were found to be the best membrane solvents as far as membrane stability and permeation of lactic acid are concerned. CYPHOS IL-109 and CYPHOS IL-111 were found to be unsuitable, as they leak out from the pores of the supported liquid membrane (SLM), thereby allowing free transport of lactic acid as well as hydrochloric acid. CYPHOS IL-102 was found to be the most adequate (Permeation rate = 60.41%) among these ionic liquids as far as the separation of lactic acid is concerned. The permeation mechanisms, by which ionic liquid-water complexes act as the carrier of lactate and hydrochloric acid, were proposed. The experimental permeation results have been obtained as opposed to the expected values from the solution-diffusion mechanism. PMID:24957613

  11. Inhibition of beta-amino acid transport by diamide does not involve the brush border membrane surface

    SciTech Connect

    Chesney, R.W.; Gusowski, N.; Albright, P.

    1985-01-01

    Diamide (dicarboxylic acid bis-(N,N-dimethylamide) has been shown in previous studies to block the uptake of the beta-amino acid taurine at its high affinity transport site in rat renal cortex slices. Diamide may act by increasing the efflux of taurine from the slice. Studies performed in rat slices again indicate enhanced efflux over 8-12 minutes. The time course of reduced glutathione (GSH) depletion from renal cortex is similar, indicating a potential interaction between GSH depletion and inhibition of taurine accumulation. The effect of 9 mM diamide on the Na+ -dependent accumulation of taurine (10 and 250 microM) by brush border membrane vesicles was examined, and the taurine uptake value both initially and at equilibrium was the same in the presence and absence of diamide. Isolation of the brush border surface and subsequent transport studies of taurine are not influenced by diamide. Thus, diamide inhibition of taurine uptake does not involve physiochemical alteration of the membrane surface where active amino acid transport occurs, despite the thiol-oxidizing properties of this agent. Further, these studies suggest that diamide either acts at the basolateral surface, rather than the brush border surface of rat renal cortex or requires the presence of an intact tubule, capable of metabolism, prior to its inhibitory action.

  12. Graphene-sensitized microporous membrane/solvent microextraction for the preconcentration of cinnamic acid derivatives in Rhizoma Typhonii.

    PubMed

    Xing, Rongrong; Hu, Shuang; Chen, Xuan; Bai, Xiaohong

    2014-09-01

    A novel graphene-sensitized microporous membrane/solvent microextraction method named microporous membrane/graphene/solvent synergistic microextraction, coupled with high-performance liquid chromatography and UV detection, was developed and introduced for the extraction and determination of three cinnamic acid derivatives in Rhizoma Typhonii. Several factors affecting performance were investigated and optimized, including the types of graphene and extraction solvent, concentration of graphene dispersed in octanol, sample phase pH, ionic strength, stirring rate, extraction time, extraction temperature, and sample volume. Under optimized conditions, the enrichment factors of cinnamic acid derivatives ranged from 75 to 269. Good linearities were obtained from 0.01 to 10 μg/mL for all analytes with regression coefficients between 0.9927 and 0.9994. The limits of quantification were <1 ng/mL, and satisfactory recoveries (99-104%) and precision (1.1-10.8%) were also achieved. The synergistic microextraction mechanism based on graphene sensitization was analyzed and described. The experimental results showed that the method was simple, sensitive, practical, and effective for the preconcentration and determination of cinnamic acid derivatives in Rhizoma Typhonii.

  13. In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water.

    PubMed

    Varanusupakul, Pakorn; Vora-Adisak, Narongchai; Pulpoka, Bancha

    2007-08-13

    An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 degrees C for 60 min with 20% Na2SO4. The linear calibration curves were observed for the concentrations ranging from 1 to 300 microg L(-1) with the correlation coefficients (R2) being greater than 0.99. The method detection limits of most analytes were below 1 microg L(-1) except DCAA and MCAA that were 2 and 18 microg L(-1), respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water. PMID:17693310

  14. Remodeling of the Vibrio cholerae membrane by incorporation of exogenous fatty acids from host and aquatic environments

    PubMed Central

    Giles, David K.; Hankins, Jessica V.; Guan, Ziqiang; Trent, M. Stephen

    2011-01-01

    Summary The Gram-negative bacteria Vibrio cholerae poses significant public health concerns by causing an acute intestinal infection afflicting millions of people each year. V. cholerae motility, as well as virulence factor expression and outer membrane protein production, have been shown to be affected by bile (Childers & Klose, 2007). The current study examines the effects of bile on V. cholerae phospholipids. Bile exposure caused significant alterations to the phospholipid profile of V. cholerae but not of other enteric pathogens. These changes consisted of a quantitative increase and migratory difference in cardiolipin, decreases in phosphatidylglycerol and phosphatidylethanolamine, and the dramatic appearance of an unknown phospholipid determined to be lyso-phosphatidylethanolamine. Major components of bile were not responsible for the observed changes, but long chain polyunsaturated fatty acids, which are minor components of bile, were shown to be incorporated into phospholipids of V. cholerae. Although the bile-induced phospholipid profile was independent of the V. cholerae virulence cascade, we identified another relevant environment in which V. cholerae assimilates unique fatty acids into its membrane phospholipids—marine sediment. Our results suggest that Vibrio species possess unique machinery conferring the ability to take up a wider range of exogenous fatty acids than other enteric bacteria. PMID:21255114

  15. Biosynthesis of C18 polyunsaturated fatty acids in microsomal membrane preparations from the filamentous fungus Mucor circinelloides.

    PubMed

    Jackson, F M; Fraser, T C; Smith, M A; Lazarus, C; Stobart, A K; Griffiths, G

    1998-03-15

    The biosynthesis of C18 polyunsaturated fatty acids has been studied in the fungus Mucor circinelloides. Microsomal membrane preparations contained delta9, delta12 and delta6 desaturase activities. The delta9 desaturase exhibited characteristics similar to those of the animal and yeast delta9 desaturases in being membrane bound and utilising stearoyl-CoA as substrate. Cytochrome b5 (a soluble form lacking the 20-amino-acid hydrophobic C-terminus) stimulated desaturation and was identified as a major cytochrome component of the membranes. A high ferricyanide reductase activity (indicative of NADH:cytochrome b5 reductase activity) coupled to inhibition by cyanide further supported the similarity with the mammalian and yeast enzymes. Time-course studies with radiolabelled oleoyl-CoA showed that the oleate [18:1(9)] was transferred to position sn-2 of phosphatidylcholine (PtdCho) and was desaturated to linoleoyl-PtdCho. Removal of the excess oleoyl-CoA from the membranes prior to addition of reductant confirmed that oleoyl-PtdCho is a substrate for the delta12 desaturase. The entry of oleate at this position of the phospholipid was facilitated by the activity of lyso-PtdCho:acyl-CoA acyltransferase (LPCAT), which readily transferred oleate from oleoyl-CoA to lyso-PtdCho. Desaturation of oleate at the sn-1 position of PtdCho was also demonstrated after the entry of oleate in to the phospholipid by the enzymes of the Kennedy pathway. Thus oleate at sn-1 and sn-2 positions served as substrate for the delta12 desaturase and is consistent with observations in oil seed tissues. LPCAT activity was substantially higher than that observed with lysophosphatidylethanolamine:acyl-CoA acyltransferase (LPEAT) indicating that oleate is less effectively channelled to phosphatidylethanolamine for linoleate synthesis. No desaturation on phosphatidylinositol could be demonstrated. Delta6 desaturase utilised linoleate at the sn-2 position of exogenously supplied PtdCho presented to the

  16. [Fatty acid composition of the lipids in human blood plasma and erythrocyte membranes during simulation of extravehicular activities of cosmonauts].

    PubMed

    Skedina, M A; Katuntsev, V P; Buravkova, L B; Naĭdina, V P

    1998-01-01

    Dynamics of the lipoacidic content of total plasma lipids and erythtocyte membranes was studied in 32 experiments with ten apparently healthy male subjects aged 27 to 41 years who were exposed to repeated decompression from the normal ground down to 40-35 kPa. For two hours of exposure to lowered pressure the subjects were breathing pure oxygen in mask and performing incremental physical work mimicking loading of the upper extremities of cosmonauts doing extravehicular activities (EVA) at the energy cost of 3 kcal/min. Decompression sessions were repeated with intervals from 3 to 5 days. In seven experiments, the subjects developed symptoms of the decompression sickness (DCS). Penetration of gas bubbles (GB) into the pulmonary artery was registered in 27 cases (84.4%). In 24 cases maximal intensity of the US signals from GB reached 3 to 4 Spencer's points. No changes in the lipidoacidic content of blood plasma or erythrocyte membranes were determined following the first exposure to decompression. BY the onset of repeated decompression, total number of lipids in erythrocyte membranes decreased from 54.6 to 40.4 mg% in the group of subjects who had not displayed DCS symptoms (n = 5) and from 51.2 to 35.2 mg% (p < 0.05) in the group of subjects with DCS symptoms (n = 5). In the subjects with DCS, polyunsaturated linoleic acid (18:2) tended to decrease against the upward trend of saturated fatty acids (16:0, 18:0). In these subjects, arachidonic acid in erythrocyte membranes (20:4) decreased following each decompression exposure and significantly increased (p < 0.05) in-between. In both groups, blood plasma showed slight fluctuations in the lipoacidic contents. These data suggest that exposure to the variety of the EVA-simulating factors may entail quite distinct but reversible modifications in the lipid metabolism in blood and the structural/functional state of erythrocyte membranes. The most marked alterations were observed in the subjects with the DCS symptoms

  17. Congener-specific organic carbon-normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluoroalkyl carboxylic and sulfonic acids.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2009-11-01

    Organic carbon-normalized soil and sediment-water partitioning coefficients (K(oc)) were estimated for all C(1) through C(8) perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acid congeners. The limited experimental K(oc) data set for the straight chain C(7) through C(10) PFCAs and C(8) and C(10) PFSAs was correlated to SPARC and ALOGPS computationally estimated octanol-water partitioning/distribution constants and used to predict K(oc) values for both branched and linear C(1) through C(8) isomers. Branched and linear congeners in this homologue range are generally expected to have K(oc) values > 1, leading to their accumulation in organic matter on sediments and soils, retardation during ground and pore water flow, and the preferential association with dissolved organic matter in aquatic systems. Both increasing perfluoroalkyl chain length and linearity increase K(oc) values with substantial intra- and inter-homologue variation and interhomologue mixing. Variability in K(oc) values among the PFCA and PFSA congeners will likely lead to an enrichment of more linear and longer-chain isomers in organic matter fractions, resulting in aqueous phases fractionated towards shorter-chain branched congeners. The expected magnitude of fractionation will require inclusion in source apportionment models and risk assessments. A comparison of representative established quantitative structure property relationships for estimating K(oc) values from octanol-water partitioning constants suggests that these equilibrium partitioning frameworks may be applicable towards modeling PFCA and PFSA environmental fate processes. PMID:20183495

  18. Synthesis, characterization and fuel cell performance tests of boric acid and boron phosphate doped, sulphonated and phosphonated poly(vinyl alcohol) based composite membranes

    NASA Astrophysics Data System (ADS)

    Şahin, Alpay; Ar, İrfan

    2015-08-01

    The aim of this study is to synthesize a composite membrane having high proton conductivity, ion exchange capacity and chemical stability. In order to achieve this aim, poly(vinyl alcohol) (PVA) based composite membranes are synthesized by using classic sol-gel method. Boric acid (H3BO3) and boron phosphate (BPO4) are added to the membrane matrix in different ratios in order to enhance the membrane properties. Characterization tests, i.e; FT-IR analysis, mechanical strength tests, water hold-up capacities, swelling properties, ion exchange capacities, proton conductivities and fuel cell performance tests of synthesized membranes are carried out. As a result of performance experiments highest performance values are obtained for the membrane containing 15% boron phosphate at 0.6 V and 750 mA/cm2. Water hold-up capacity, swelling ratio, ion exchange capacity and proton conductivity of this membrane are found as 56%, 8%, 1.36 meq/g and 0.37 S/cm, respectively. These values are close to the values obtained ones for perfluorosulphonic acid membranes. Therefore this membrane can be regarded as a promising candidate for usage in fuel cells.

  19. Separation of copper ions from iron ions using PVA-g-(acrylic acid/N-vinyl imidazole) membranes prepared by radiation-induced grafting.

    PubMed

    Ajji, Zaki; Ali, Ali M

    2010-01-15

    Acrylic acid (AAc), N-vinyl imidazole (Azol) and their binary mixtures were graft copolymerized onto poly(vinyl alcohol) membranes using gamma irradiation. The ability of the grafted membranes to separate Cu ions from Fe ions was investigated with respect to the grafting yield and the pH of the feed solution. The data showed that the diffusion of copper ions from the feed compartment to the receiver compartment depends on the grafting yield of the membranes and the pH of the feed solution. To the contrary, iron ions did not diffuse through the membranes of all grafting yields. However, a limited amount of iron ions diffused in strong acidic medium. This study shows that the prepared membranes could be considered for the separation of copper ions from iron ions. The temperature of thermal decomposition of pure PVA-g-AAc/Azol membrane, PVA-g-AAc/Azol membrane containing copper ions, and PVA-g-AAc/Azol membrane containing iron ions were determined using TGA analyzer. It was shown that the presence of Cu and Fe ions increases the decomposition temperature, and the membranes bonded with iron ions are more stable than those containing copper ions. PMID:19836882

  20. Serum and erythrocyte membrane phospholipids fatty acid composition in hyperlipidemia: effects of dietary intervention and combined diet and fibrate therapy.

    PubMed

    Ristic-Medic, Danijela; Suzic, Slavica; Vucic, Vesna; Takic, Marija; Tepsic, Jasna; Glibetic, Marija

    2009-01-01

    Hyperlipidemia is found to be associated with changes in fatty acid (FA) profiles. The aim of this study was to investigate the effects of AHA-Step-1 dietary treatment and combination of fibrates (gemfibrozil) with dietary intervention on serum and erythrocyte phospholipid FA composition in human hyperlipidemia. 78 study participants with hyperlipidemia were divided in two groups. In D group (n = 41) subjects followed AHA-Step-1 diet (<30% of total from fat, <10% of energy from saturated fat, and <300 mg cholesterol per day). D+F group (n = 37) followed Step-1 diet and were receiving gemfibrozil (300 mg/twice per day). Serum lipid levels and phospholipid serum and erythrocyte FA compositions were analyzed at the beginning and after 12 weeks of treatment. Alteration in serum and erythrocyte phospholipid FA profile were found in both groups. After both treatments we found significantly higher serum phospholipid percentages of n-3, n-6 and total polyunsaturated FA. Linoleic (LA, n-6) and docosahexaenoic acid (DHA, n-3) were higher in D group, but arachidonic (AA, n-6) and linolenic acid (LNA, n-3) in D+F group. In erythrocyte phospholipid levels of stearic, palmitoleic (16 : 1, n-7) and LA were significantly higher in D group, but palmitic acid, AA and eicosapentaenoic acid (EPA, n-3) in D+F group. Stronger correlation between serum triglycerides with EPA and DHA in erythrocyte membrane phospholipid was found in D+F group. Markedly increased percentage of AA in serum and erythrocyte membrane phospholipid in hyperlipidemic patients receiving gemfibrozil on Step-1 diet is especially important for physiological functions (inflammation, vascular tone, hemostasis etc.) in relation to cardiometabolic risk.

  1. Pore formation mechanism of porous poly(DL-lactic acid) matrix membrane.

    PubMed

    Phaechamud, Thawatchai; Chitrattha, Sasiprapa

    2016-04-01

    Porous PLA structure has been widely used in cell transplantation, drug carrier and wound dressing. The porous structure can be controlled depending on the choice of the polymer, solvent, nonsolvent and preparation parameters. In this study, the porous PLA matrix membranes were prepared by adding PEG 400 in PLA solution using dichloromethane (DCM) as solvent prior to casting. The influence of other liquids as co-solvent on pore formation and the structural change during membrane formation were evaluated. The co-solvents affected both porous topography and mechanical properties of PLA membrane. The porous matrix were produced when the non-solvent of PLA was used as co-solvent. Cryo-SEM micrographs revealed that PEG 400 still remained in the PLA porous matrix membrane. From the tracking of the structural change during film formation, the PLA-PEG solution changed into porous structure by liquid liquid phase separation and solidification processes, respectively. Thermogravimetric analysis revealed that PLA-PEG in DCM solution exhibited the two-step of weight loss, the first step occurred from DCM evaporation and the second step occurred from the degradation of PLA-PEG matrix. The liquid-liquid phase separation and solidification started when the amount of DCM was higher than PEG 400 for 2.67 folds and DCM amount was equal to that of PEG 400, respectively. These results could clarify the pore formation mechanism of porous PLA membrane and will be useful for the further investigation and application. PMID:26838905

  2. Cognitive performance in older adults is inversely associated with fish consumption but not erythrocyte membrane n-3 fatty acids.

    PubMed

    Danthiir, Vanessa; Hosking, Diane; Burns, Nicholas R; Wilson, Carlene; Nettelbeck, Ted; Calvaresi, Eva; Clifton, Peter; Wittert, Gary A

    2014-03-01

    Higher n-3 (ω-3) polyunsaturated fatty acids (PUFAs) and fish intake may help maintain cognitive function in older age. However, evidence is inconsistent; few studies have examined the relation in cognitively healthy individuals across numerous cognitive domains, and none to our knowledge have considered lifetime fish intake. We examined associations between multiple domains of cognition and erythrocyte membrane n-3 PUFA proportions and historical and contemporary fish intake in 390 normal older adults, analyzing baseline data from the Older People, Omega-3, and Cognitive Health trial. We measured n-3 PUFA in erythrocyte membranes, and we assessed historical and contemporary fish intake by food-frequency questionnaires. We assessed cognitive performance on reasoning, working memory, short-term memory, retrieval fluency, perceptual speed, simple/choice reaction time, speed of memory-scanning, reasoning speed, inhibition, and psychomotor speed. Cognitive outcomes for each construct were factor scores from confirmatory factor analysis. Multiple linear regression models controlled for a number of potential confounding factors, including age, education, sex, apolipoprotein E-ε 4 allele, physical activity, smoking, alcohol intake, socioeconomic variables, and other health-related variables. Higher erythrocyte membrane eicosapaentonoic acid proportions predicted slower perceptual and reasoning speed in females, which was attenuated once current fish intake was controlled. No other associations were present between n-3 PUFA proportions and cognitive performance. Higher current fish consumption predicted worse performance on several cognitive speed constructs. Greater fish consumption in childhood predicted slower perceptual speed and simple/choice reaction time. We found no evidence to support the hypothesis that higher proportions of long-chain n-3 fatty acids or fish intake benefits cognitive performance in normal older adults.

  3. A heteromeric membrane-bound prenyltransferase complex from hop catalyzes three sequential aromatic prenylations in the bitter acid pathway.

    PubMed

    Li, Haoxun; Ban, Zhaonan; Qin, Hao; Ma, Liya; King, Andrew J; Wang, Guodong

    2015-03-01

    Bitter acids (α and β types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the β-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in β-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop. PMID:25564559

  4. Membrane omega-3 Fatty Acid deficiency as a preventable risk factor for comorbid coronary heart disease in major depressive disorder.

    PubMed

    McNamara, Robert K

    2009-01-01

    Major depression disorder (MDD) significantly increases the risk for coronary heart disease (CHD) which is a leading cause of mortality in patients with MDD. Moreover, depression is frequently observed in a subset of patients following acute coronary syndrome (ACS) and increases risk for mortality. Here evidence implicating omega-3 (n-3) fatty acid deficiency in the pathoaetiology of CHD and MDD is reviewed, and the hypothesis that n-3 fatty acid deficiency is a preventable risk factor for CHD comorbidity in MDD patients is evaluated. This hypothesis is supported by cross-national and cross-sectional epidemiological surveys finding an inverse correlation between n-3 fatty acid status and prevalence rates of both CHD and MDD, prospective studies finding that lower dietary or membrane EPA+DHA levels increase risk for both MDD and CHD, case-control studies finding that the n-3 fatty acid status of MDD patients places them at high risk for emergent CHD morbidity and mortality, meta-analyses of controlled n-3 fatty acid intervention studies finding significant advantage over placebo for reducing depression symptom severity in MDD patients, and for secondary prevention of cardiac events in CHD patients, findings that n-3 fatty acid status is inversely correlated with other documented CHD risk factors, and patients diagnosed with MDD after ACS exhibit significantly lower n-3 fatty acid status compared with nondepressed ACS patients. This body of evidence provides strong support for future studies to evaluate the effects of increasing dietary n-3 fatty acid status on CHD comorbidity and mortality in MDD patients.

  5. Effects of smoking on fatty acid composition of phospholipid sperm membrane and the malondialdehyde levels in human seminal plasma.

    PubMed

    Štramová, X; Čegan, A; Hampl, R; Kanďár, R

    2015-11-01

    The aim of this study was to investigate fatty acids composition of sperm phospholipids, level of lipoperoxidation represented by malondialdehyde and to examine differences between recent smokers and nonsmokers. The levels of malondialdehyde were in the group of all patients 1.51 ± 0.56 μmol l(-1) , in smokers 1.36 ± 0.59 μmol l(-1) and in nonsmokers 1.53 ± 0.55 μmol l(-1) . Total sperm membrane phospholipid fatty acids were profiled into several groups, saturated acids (in smokers 61.86 ± 9.02%, in nonsmokers 61.20 ± 11.66%), polyunsaturated acids n-3 (in smokers 12.62 ± 8.18%, in nonsmokers 14.28 ± 13.65%), polyunsaturated acids n-6 (in smokers 9.13 ± 4.37%, in nonsmokers 10.10 ± 3.79%) and other acids (in smokers 14.36 ± 3.94%, in nonsmokers 13.88 ± 2.31%). Significant correlations were found between the level of malondialdehyde (MDA) and total sperm motility in all patients (r = -0.358, P = 0.013), between both the level of MDA and progressive motility (r = -0.465, P = 0.001) and between the level of MDA and total motility (r = -0.382, P = 0.037) in nonsmokers. There were no statistically significant differences between composition of sperm phospholipid important fatty acids in smokers and nonsmokers. Significant correlations between selected sperm fatty acids and sperm motility and morphology in smokers and nonsmokers were not observed. PMID:25311153

  6. Effects of smoking on fatty acid composition of phospholipid sperm membrane and the malondialdehyde levels in human seminal plasma.

    PubMed

    Štramová, X; Čegan, A; Hampl, R; Kanďár, R

    2015-11-01

    The aim of this study was to investigate fatty acids composition of sperm phospholipids, level of lipoperoxidation represented by malondialdehyde and to examine differences between recent smokers and nonsmokers. The levels of malondialdehyde were in the group of all patients 1.51 ± 0.56 μmol l(-1) , in smokers 1.36 ± 0.59 μmol l(-1) and in nonsmokers 1.53 ± 0.55 μmol l(-1) . Total sperm membrane phospholipid fatty acids were profiled into several groups, saturated acids (in smokers 61.86 ± 9.02%, in nonsmokers 61.20 ± 11.66%), polyunsaturated acids n-3 (in smokers 12.62 ± 8.18%, in nonsmokers 14.28 ± 13.65%), polyunsaturated acids n-6 (in smokers 9.13 ± 4.37%, in nonsmokers 10.10 ± 3.79%) and other acids (in smokers 14.36 ± 3.94%, in nonsmokers 13.88 ± 2.31%). Significant correlations were found between the level of malondialdehyde (MDA) and total sperm motility in all patients (r = -0.358, P = 0.013), between both the level of MDA and progressive motility (r = -0.465, P = 0.001) and between the level of MDA and total motility (r = -0.382, P = 0.037) in nonsmokers. There were no statistically significant differences between composition of sperm phospholipid important fatty acids in smokers and nonsmokers. Significant correlations between selected sperm fatty acids and sperm motility and morphology in smokers and nonsmokers were not observed.

  7. Adaptive changes in fatty acid profile of erythrocyte membrane in relation to plasma and red cell metabolic changes in chronic alcoholic men.

    PubMed

    Maturu, Paramahamsa; Varadacharyulu, Nallanchakravarthula

    2012-07-01

    Chronic alcohol consumption is a major reason for several human diseases, and alcoholism has been associated with a variety of societal problems. Changes in fatty acid metabolism in alcoholics and its effects leading to membrane damage are largely unknown. Therefore, we aimed to investigate the fatty acid composition of erythrocyte membrane phospholipids in relation with plasma lipid profile and other plasma metabolites in chronic alcoholics in comparison with controls. We systematically measured the levels of glucose, lactate and pyruvate in the blood and free amino acids, free fatty acids, mucoproteins and glycolipids, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very-low-density lipoprotein (VLDL) cholesterol and triglycerides (TG) in plasma of chronic alcoholics and controls. Furthermore, we measured fatty acid composition by gas chromatographic analysis. The fatty acid composition clearly revealed certain changes in chronic alcoholic erythrocyte membrane, chiefly increments in C16:0 and a decrease in C22:4 and C22:6 fatty acids besides the presence of unidentified fatty acids, probably C-24 or C-26 fatty acids. In addition, a significant increase in blood lactate, decrease in blood pyruvate and increased levels of free amino acids and free fatty acids, mucoproteins, VLDL cholesterol, TG and HDL-C in chronic alcoholics were observed with no significant change in plasma TC, LDL-C and glycolipids when compared with controls. Alcohol-induced alterations in plasma and erythrocyte membranes of chronic alcoholics in the present study might be an adaptive response to counteract the deleterious effects of alcohol. The implications of our findings warrant further investigation and needs further in-depth study to explore the mechanisms of alcohol-induced membrane changes.

  8. Perfluoroalkyl phosphonic and phosphinic acids as proton conductors for anhydrous proton-exchange membranes.

    PubMed

    Herath, Mahesha B; Creager, Stephen E; Kitaygorodskiy, Alex; DesMarteau, Darryl D

    2010-09-10

    A study of proton-transport rates and mechanisms under anhydrous conditions using a series of acid model compounds, analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, sulfonic, and carboxylic acid protogenic groups, is reported. Model compounds are characterized with respect to proton conductivity, viscosity, proton, and anion (conjugate base) self-diffusion coefficients, and Hammett acidity. The highest conductivities, and also the highest viscosities, are observed for the phosphonic and phosphinic acid model compounds. Arrhenius analysis of conductivity and viscosity for these two acids reveals much lower activation energies for ion transport than for viscous flow. Additionally, the proton self-diffusion coefficients are much higher than the conjugate-base self-diffusion coefficients for these two acids. Taken together, these data suggest that anhydrous proton transport in the phosphonic and phosphinic acid model compounds occurs primarily by a structure-diffusion, hopping-based mechanism rather than a vehicle mechanism. Further analysis of ionic conductivity and ion self-diffusion rates by using the Nernst-Einstein equation reveals that the phosphonic and phosphinic acid model compounds are relatively highly dissociated even under anhydrous conditions. In contrast, sulfonic and carboxylic acid-based systems exhibit relatively low degrees of dissociation under anhydrous conditions. These findings suggest that fluoroalkyl phosphonic and phosphinic acids are good candidates for further development as anhydrous, high-temperature proton conductors.

  9. Graphene oxide induces plasma membrane damage, reactive oxygen species accumulation and fatty acid profiles change in Pichia pastoris.

    PubMed

    Zhang, Meng; Yu, Qilin; Liang, Chen; Liu, Zhe; Zhang, Biao; Li, Mingchun

    2016-10-01

    During the past couple of years, graphene nanomaterials were extremely popular among the scientists due to the promising properties in many aspects. Before the materials being well applied, we should first focus on their biosafety and toxicity. In this study, we investigated the toxicity of synthesized graphene oxide (GO) against the model industrial organism Pichia pastoris. We found that the synthesized GO showed dose-dependent toxicity to P. pastoris, through cell membrane damage and intracellular reactive oxygen species (ROS) accumulation. In response to these cell stresses, cells had normal unsaturated fatty acid (UFA) levels but increased contents of polyunsaturated fatty acid (PUFA) with up-regulation of UFA synthesis-related genes on the transcriptional level, which made it overcome the stress under GO attack. Two UFA defective strains (spt23Δ and fad12Δ) were used to demonstrate the results above. Hence, this study suggested a close connection between PUFAs and cell survival against GO. PMID:27376352

  10. Highly Efficient Catalysis of Azo Dyes Using Recyclable Silver Nanoparticles Immobilized on Tannic Acid-Grafted Eggshell Membrane

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojing; Liang, Miao; Liu, Mingyue; Su, Rongxin; Wang, Mengfan; Qi, Wei; He, Zhimin

    2016-10-01

    In this study, a facile one-step synthesis of a novel nanocomposite catalytic film was developed based on silver nanoparticles (AgNPs) immobilized in tannic acid-modified eggshell membrane (Tan-ESM). Tannic acid, as a typical plant polyphenol from oak wood, was first grafted onto ESM fibers to serve as both the reductant and the stabilizer during the synthesis of AgNPs. The morphology, constitution, and thermal stability of the resulting AgNPs@Tan-ESM composites were fully characterized to explain the excellent catalytic efficiency of AgNPs@Tan-ESM composites. These composite catalysts were applied to the degradation of azo dyes which exhibited the high catalytic activity toward Congo red and methyl orange according to the kinetic curves. More importantly, they can be easily recovered and reused for many times because of their good stability.

  11. The effect of porosity on performance of phosphoric acid doped polybenzimidazole polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Celik, Muhammet; Genc, Gamze; Elden, Gulsah; Yapici, Huseyin

    2016-03-01

    A polybenzimidazole (PBI) based polymer electrolyte fuel cells, which called high temperature polymer electrolyte fuel cells (HT-PEMS), operate at higher temperatures (120-200°C) than conventional PEM fuel cells. Although it is known tha